diff --git a/src/Header/AcceptRanges.php b/src/Header/AcceptRanges.php
index 5b094a5033..4ae61a6761 100644
--- a/src/Header/AcceptRanges.php
+++ b/src/Header/AcceptRanges.php
@@ -27,14 +27,12 @@ public static function fromString($headerLine)
             );
         }
 
-        $header = new static($value);
-
-        return $header;
+        return new static($value);
     }
 
     public function __construct($rangeUnit = null)
     {
-        if ($rangeUnit) {
+        if ($rangeUnit !== null) {
             $this->setRangeUnit($rangeUnit);
         }
     }
@@ -58,7 +56,7 @@ public function setRangeUnit($rangeUnit)
 
     public function getRangeUnit()
     {
-        return $this->rangeUnit;
+        return (string) $this->rangeUnit;
     }
 
     public function toString()
diff --git a/src/Header/Age.php b/src/Header/Age.php
index 7d0bab82e1..2419a99289 100644
--- a/src/Header/Age.php
+++ b/src/Header/Age.php
@@ -37,14 +37,12 @@ public static function fromString($headerLine)
             throw new Exception\InvalidArgumentException('Invalid header line for Age string: "' . $name . '"');
         }
 
-        $header = new static($value);
-
-        return $header;
+        return new static($value);
     }
 
     public function __construct($deltaSeconds = null)
     {
-        if ($deltaSeconds) {
+        if ($deltaSeconds !== null) {
             $this->setDeltaSeconds($deltaSeconds);
         }
     }
@@ -62,11 +60,11 @@ public function getFieldName()
     /**
      * Get header value (number of seconds)
      *
-     * @return int
+     * @return string
      */
     public function getFieldValue()
     {
-        return $this->getDeltaSeconds();
+        return (string) $this->getDeltaSeconds();
     }
 
     /**
diff --git a/src/Header/AuthenticationInfo.php b/src/Header/AuthenticationInfo.php
index cf75caed7c..b9f24aa8e1 100644
--- a/src/Header/AuthenticationInfo.php
+++ b/src/Header/AuthenticationInfo.php
@@ -31,14 +31,12 @@ public static function fromString($headerLine)
         }
 
         // @todo implementation details
-        $header = new static($value);
-
-        return $header;
+        return new static($value);
     }
 
     public function __construct($value = null)
     {
-        if ($value) {
+        if ($value !== null) {
             HeaderValue::assertValid($value);
             $this->value = $value;
         }
@@ -51,7 +49,7 @@ public function getFieldName()
 
     public function getFieldValue()
     {
-        return $this->value;
+        return (string) $this->value;
     }
 
     public function toString()
diff --git a/src/Header/Authorization.php b/src/Header/Authorization.php
index ccdfb3ed9a..caf3f22483 100644
--- a/src/Header/Authorization.php
+++ b/src/Header/Authorization.php
@@ -31,14 +31,12 @@ public static function fromString($headerLine)
         }
 
         // @todo implementation details
-        $header = new static($value);
-
-        return $header;
+        return new static($value);
     }
 
     public function __construct($value = null)
     {
-        if ($value) {
+        if ($value !== null) {
             HeaderValue::assertValid($value);
             $this->value = $value;
         }
@@ -51,7 +49,7 @@ public function getFieldName()
 
     public function getFieldValue()
     {
-        return $this->value;
+        return (string) $this->value;
     }
 
     public function toString()
diff --git a/src/Header/ContentDisposition.php b/src/Header/ContentDisposition.php
index 747505af36..19d7132102 100644
--- a/src/Header/ContentDisposition.php
+++ b/src/Header/ContentDisposition.php
@@ -31,14 +31,12 @@ public static function fromString($headerLine)
         }
 
         // @todo implementation details
-        $header = new static($value);
-
-        return $header;
+        return new static($value);
     }
 
     public function __construct($value = null)
     {
-        if ($value) {
+        if ($value !== null) {
             HeaderValue::assertValid($value);
             $this->value = $value;
         }
@@ -51,7 +49,7 @@ public function getFieldName()
 
     public function getFieldValue()
     {
-        return $this->value;
+        return (string) $this->value;
     }
 
     public function toString()
diff --git a/src/Header/ContentEncoding.php b/src/Header/ContentEncoding.php
index daeb260e0e..73d9b91865 100644
--- a/src/Header/ContentEncoding.php
+++ b/src/Header/ContentEncoding.php
@@ -30,14 +30,12 @@ public static function fromString($headerLine)
         }
 
         // @todo implementation details
-        $header = new static($value);
-
-        return $header;
+        return new static($value);
     }
 
     public function __construct($value = null)
     {
-        if ($value) {
+        if ($value !== null) {
             HeaderValue::assertValid($value);
             $this->value = $value;
         }
@@ -50,7 +48,7 @@ public function getFieldName()
 
     public function getFieldValue()
     {
-        return $this->value;
+        return (string) $this->value;
     }
 
     public function toString()
diff --git a/src/Header/ContentLanguage.php b/src/Header/ContentLanguage.php
index 320b727321..9d0016d314 100644
--- a/src/Header/ContentLanguage.php
+++ b/src/Header/ContentLanguage.php
@@ -31,14 +31,12 @@ public static function fromString($headerLine)
         }
 
         // @todo implementation details
-        $header = new static($value);
-
-        return $header;
+        return new static($value);
     }
 
     public function __construct($value = null)
     {
-        if ($value) {
+        if ($value !== null) {
             HeaderValue::assertValid($value);
             $this->value = $value;
         }
@@ -51,7 +49,7 @@ public function getFieldName()
 
     public function getFieldValue()
     {
-        return $this->value;
+        return (string) $this->value;
     }
 
     public function toString()
diff --git a/src/Header/ContentLength.php b/src/Header/ContentLength.php
index 6eee98693a..bea93e322f 100644
--- a/src/Header/ContentLength.php
+++ b/src/Header/ContentLength.php
@@ -31,9 +31,7 @@ public static function fromString($headerLine)
         }
 
         // @todo implementation details
-        $header = new static($value);
-
-        return $header;
+        return new static($value);
     }
 
     public function __construct($value = null)
@@ -51,7 +49,7 @@ public function getFieldName()
 
     public function getFieldValue()
     {
-        return $this->value;
+        return (string) $this->value;
     }
 
     public function toString()
diff --git a/src/Header/ContentMD5.php b/src/Header/ContentMD5.php
index c551e39dfb..db56ffd0a5 100644
--- a/src/Header/ContentMD5.php
+++ b/src/Header/ContentMD5.php
@@ -28,14 +28,12 @@ public static function fromString($headerLine)
         }
 
         // @todo implementation details
-        $header = new static($value);
-
-        return $header;
+        return new static($value);
     }
 
     public function __construct($value = null)
     {
-        if ($value) {
+        if ($value !== null) {
             HeaderValue::assertValid($value);
             $this->value = $value;
         }
@@ -48,7 +46,7 @@ public function getFieldName()
 
     public function getFieldValue()
     {
-        return $this->value;
+        return (string) $this->value;
     }
 
     public function toString()
diff --git a/src/Header/ContentRange.php b/src/Header/ContentRange.php
index 077f2be835..536fd9e4d6 100644
--- a/src/Header/ContentRange.php
+++ b/src/Header/ContentRange.php
@@ -31,14 +31,12 @@ public static function fromString($headerLine)
         }
 
         // @todo implementation details
-        $header = new static($value);
-
-        return $header;
+        return new static($value);
     }
 
     public function __construct($value = null)
     {
-        if ($value) {
+        if ($value !== null) {
             HeaderValue::assertValid($value);
             $this->value = $value;
         }
@@ -51,7 +49,7 @@ public function getFieldName()
 
     public function getFieldValue()
     {
-        return $this->value;
+        return (string) $this->value;
     }
 
     public function toString()
diff --git a/src/Header/ContentTransferEncoding.php b/src/Header/ContentTransferEncoding.php
index 949fc7fe9d..2134297667 100644
--- a/src/Header/ContentTransferEncoding.php
+++ b/src/Header/ContentTransferEncoding.php
@@ -31,14 +31,12 @@ public static function fromString($headerLine)
         }
 
         // @todo implementation details
-        $header = new static(strtolower($value));
-
-        return $header;
+        return new static(strtolower($value));
     }
 
     public function __construct($value = null)
     {
-        if ($value) {
+        if ($value !== null) {
             HeaderValue::assertValid($value);
             $this->value = $value;
         }
@@ -51,7 +49,7 @@ public function getFieldName()
 
     public function getFieldValue()
     {
-        return $this->value;
+        return (string) $this->value;
     }
 
     public function toString()
diff --git a/src/Header/ContentType.php b/src/Header/ContentType.php
index b5b2522a64..86a7666144 100644
--- a/src/Header/ContentType.php
+++ b/src/Header/ContentType.php
@@ -69,7 +69,7 @@ public static function fromString($headerLine)
 
     public function __construct($value = null, $mediaType = null)
     {
-        if ($value) {
+        if ($value !== null) {
             HeaderValue::assertValid($value);
             $this->value = $value;
         }
@@ -146,7 +146,7 @@ public function getFieldName()
     public function getFieldValue()
     {
         if (null !== $this->value) {
-            return $this->value;
+            return (string) $this->value;
         }
         return $this->assembleValue();
     }
@@ -172,7 +172,7 @@ public function setMediaType($mediaType)
      */
     public function getMediaType()
     {
-        return $this->mediaType;
+        return (string) $this->mediaType;
     }
 
     /**
diff --git a/src/Header/Etag.php b/src/Header/Etag.php
index 395fbfc97e..8d553b5b9b 100644
--- a/src/Header/Etag.php
+++ b/src/Header/Etag.php
@@ -28,14 +28,12 @@ public static function fromString($headerLine)
         }
 
         // @todo implementation details
-        $header = new static($value);
-
-        return $header;
+        return new static($value);
     }
 
     public function __construct($value = null)
     {
-        if ($value) {
+        if ($value !== null) {
             HeaderValue::assertValid($value);
             $this->value = $value;
         }
@@ -48,7 +46,7 @@ public function getFieldName()
 
     public function getFieldValue()
     {
-        return $this->value;
+        return (string) $this->value;
     }
 
     public function toString()
diff --git a/src/Header/Expect.php b/src/Header/Expect.php
index 1dca3f3063..37f934a7ad 100644
--- a/src/Header/Expect.php
+++ b/src/Header/Expect.php
@@ -28,14 +28,12 @@ public static function fromString($headerLine)
         }
 
         // @todo implementation details
-        $header = new static($value);
-
-        return $header;
+        return new static($value);
     }
 
     public function __construct($value = null)
     {
-        if ($value) {
+        if ($value !== null) {
             HeaderValue::assertValid($value);
             $this->value = $value;
         }
@@ -48,7 +46,7 @@ public function getFieldName()
 
     public function getFieldValue()
     {
-        return $this->value;
+        return (string) $this->value;
     }
 
     public function toString()
diff --git a/src/Header/From.php b/src/Header/From.php
index 5da35fa3ae..277001945f 100644
--- a/src/Header/From.php
+++ b/src/Header/From.php
@@ -28,14 +28,12 @@ public static function fromString($headerLine)
         }
 
         // @todo implementation details
-        $header = new static($value);
-
-        return $header;
+        return new static($value);
     }
 
     public function __construct($value = null)
     {
-        if ($value) {
+        if ($value !== null) {
             HeaderValue::assertValid($value);
             $this->value = $value;
         }
@@ -48,7 +46,7 @@ public function getFieldName()
 
     public function getFieldValue()
     {
-        return $this->value;
+        return (string) $this->value;
     }
 
     public function toString()
diff --git a/src/Header/Host.php b/src/Header/Host.php
index f796f01181..dbf5c27dc2 100644
--- a/src/Header/Host.php
+++ b/src/Header/Host.php
@@ -28,14 +28,12 @@ public static function fromString($headerLine)
         }
 
         // @todo implementation details
-        $header = new static($value);
-
-        return $header;
+        return new static($value);
     }
 
     public function __construct($value = null)
     {
-        if ($value) {
+        if ($value !== null) {
             HeaderValue::assertValid($value);
             $this->value = $value;
         }
@@ -48,7 +46,7 @@ public function getFieldName()
 
     public function getFieldValue()
     {
-        return $this->value;
+        return (string) $this->value;
     }
 
     public function toString()
diff --git a/src/Header/IfMatch.php b/src/Header/IfMatch.php
index 6724093074..d2d6e6ccb3 100644
--- a/src/Header/IfMatch.php
+++ b/src/Header/IfMatch.php
@@ -28,14 +28,12 @@ public static function fromString($headerLine)
         }
 
         // @todo implementation details
-        $header = new static($value);
-
-        return $header;
+        return new static($value);
     }
 
     public function __construct($value = null)
     {
-        if ($value) {
+        if ($value !== null) {
             HeaderValue::assertValid($value);
             $this->value = $value;
         }
@@ -48,7 +46,7 @@ public function getFieldName()
 
     public function getFieldValue()
     {
-        return $this->value;
+        return (string) $this->value;
     }
 
     public function toString()
diff --git a/src/Header/IfNoneMatch.php b/src/Header/IfNoneMatch.php
index 3514e99b29..9e00f9d8aa 100644
--- a/src/Header/IfNoneMatch.php
+++ b/src/Header/IfNoneMatch.php
@@ -31,14 +31,12 @@ public static function fromString($headerLine)
         }
 
         // @todo implementation details
-        $header = new static($value);
-
-        return $header;
+        return new static($value);
     }
 
     public function __construct($value = null)
     {
-        if ($value) {
+        if ($value !== null) {
             HeaderValue::assertValid($value);
             $this->value = $value;
         }
@@ -51,7 +49,7 @@ public function getFieldName()
 
     public function getFieldValue()
     {
-        return $this->value;
+        return (string) $this->value;
     }
 
     public function toString()
diff --git a/src/Header/IfRange.php b/src/Header/IfRange.php
index 3ed5a3823a..172e71d62f 100644
--- a/src/Header/IfRange.php
+++ b/src/Header/IfRange.php
@@ -28,14 +28,12 @@ public static function fromString($headerLine)
         }
 
         // @todo implementation details
-        $header = new static($value);
-
-        return $header;
+        return new static($value);
     }
 
     public function __construct($value = null)
     {
-        if ($value) {
+        if ($value !== null) {
             HeaderValue::assertValid($value);
             $this->value = $value;
         }
@@ -48,7 +46,7 @@ public function getFieldName()
 
     public function getFieldValue()
     {
-        return $this->value;
+        return (string) $this->value;
     }
 
     public function toString()
diff --git a/src/Header/KeepAlive.php b/src/Header/KeepAlive.php
index 26f6337443..3d72e4a7bf 100644
--- a/src/Header/KeepAlive.php
+++ b/src/Header/KeepAlive.php
@@ -28,14 +28,12 @@ public static function fromString($headerLine)
         }
 
         // @todo implementation details
-        $header = new static($value);
-
-        return $header;
+        return new static($value);
     }
 
     public function __construct($value = null)
     {
-        if ($value) {
+        if ($value !== null) {
             HeaderValue::assertValid($value);
             $this->value = $value;
         }
@@ -48,7 +46,7 @@ public function getFieldName()
 
     public function getFieldValue()
     {
-        return $this->value;
+        return (string) $this->value;
     }
 
     public function toString()
diff --git a/src/Header/MaxForwards.php b/src/Header/MaxForwards.php
index 7ec7d780fa..622b659cb7 100644
--- a/src/Header/MaxForwards.php
+++ b/src/Header/MaxForwards.php
@@ -31,14 +31,12 @@ public static function fromString($headerLine)
         }
 
         // @todo implementation details
-        $header = new static($value);
-
-        return $header;
+        return new static($value);
     }
 
     public function __construct($value = null)
     {
-        if ($value) {
+        if ($value !== null) {
             HeaderValue::assertValid($value);
             $this->value = $value;
         }
@@ -51,7 +49,7 @@ public function getFieldName()
 
     public function getFieldValue()
     {
-        return $this->value;
+        return (string) $this->value;
     }
 
     public function toString()
diff --git a/src/Header/Origin.php b/src/Header/Origin.php
index 98c8ba9662..c8143d52a6 100644
--- a/src/Header/Origin.php
+++ b/src/Header/Origin.php
@@ -42,7 +42,7 @@ public static function fromString($headerLine)
      */
     public function __construct($value = null)
     {
-        if ($value) {
+        if ($value !== null) {
             HeaderValue::assertValid($value);
             $this->value = $value;
         }
@@ -55,7 +55,7 @@ public function getFieldName()
 
     public function getFieldValue()
     {
-        return $this->value;
+        return (string) $this->value;
     }
 
     public function toString()
diff --git a/src/Header/Pragma.php b/src/Header/Pragma.php
index 8017c1b7cb..a23bf15227 100644
--- a/src/Header/Pragma.php
+++ b/src/Header/Pragma.php
@@ -28,14 +28,12 @@ public static function fromString($headerLine)
         }
 
         // @todo implementation details
-        $header = new static($value);
-
-        return $header;
+        return new static($value);
     }
 
     public function __construct($value = null)
     {
-        if ($value) {
+        if ($value !== null) {
             HeaderValue::assertValid($value);
             $this->value = $value;
         }
@@ -48,7 +46,7 @@ public function getFieldName()
 
     public function getFieldValue()
     {
-        return $this->value;
+        return (string) $this->value;
     }
 
     public function toString()
diff --git a/src/Header/ProxyAuthenticate.php b/src/Header/ProxyAuthenticate.php
index d39740b8dc..9e0026b5e3 100644
--- a/src/Header/ProxyAuthenticate.php
+++ b/src/Header/ProxyAuthenticate.php
@@ -31,14 +31,12 @@ public static function fromString($headerLine)
         }
 
         // @todo implementation details
-        $header = new static($value);
-
-        return $header;
+        return new static($value);
     }
 
     public function __construct($value = null)
     {
-        if ($value) {
+        if ($value !== null) {
             HeaderValue::assertValid($value);
             $this->value = $value;
         }
@@ -51,7 +49,7 @@ public function getFieldName()
 
     public function getFieldValue()
     {
-        return $this->value;
+        return (string) $this->value;
     }
 
     public function toString()
diff --git a/src/Header/ProxyAuthorization.php b/src/Header/ProxyAuthorization.php
index e7add19ffb..f3f01e468a 100644
--- a/src/Header/ProxyAuthorization.php
+++ b/src/Header/ProxyAuthorization.php
@@ -31,14 +31,12 @@ public static function fromString($headerLine)
         }
 
         // @todo implementation details
-        $header = new static($value);
-
-        return $header;
+        return new static($value);
     }
 
     public function __construct($value = null)
     {
-        if ($value) {
+        if ($value !== null) {
             HeaderValue::assertValid($value);
             $this->value = $value;
         }
@@ -51,7 +49,7 @@ public function getFieldName()
 
     public function getFieldValue()
     {
-        return $this->value;
+        return (string) $this->value;
     }
 
     public function toString()
diff --git a/src/Header/Range.php b/src/Header/Range.php
index b0112b2c57..289da79444 100644
--- a/src/Header/Range.php
+++ b/src/Header/Range.php
@@ -28,14 +28,12 @@ public static function fromString($headerLine)
         }
 
         // @todo implementation details
-        $header = new static($value);
-
-        return $header;
+        return new static($value);
     }
 
     public function __construct($value = null)
     {
-        if ($value) {
+        if ($value !== null) {
             HeaderValue::assertValid($value);
             $this->value = $value;
         }
@@ -48,7 +46,7 @@ public function getFieldName()
 
     public function getFieldValue()
     {
-        return $this->value;
+        return (string) $this->value;
     }
 
     public function toString()
diff --git a/src/Header/Refresh.php b/src/Header/Refresh.php
index 3d3a250b4f..0f47b901be 100644
--- a/src/Header/Refresh.php
+++ b/src/Header/Refresh.php
@@ -28,14 +28,12 @@ public static function fromString($headerLine)
         }
 
         // @todo implementation details
-        $header = new static($value);
-
-        return $header;
+        return new static($value);
     }
 
     public function __construct($value = null)
     {
-        if ($value) {
+        if ($value !== null) {
             HeaderValue::assertValid($value);
             $this->value = $value;
         }
@@ -48,7 +46,7 @@ public function getFieldName()
 
     public function getFieldValue()
     {
-        return $this->value;
+        return (string) $this->value;
     }
 
     public function toString()
diff --git a/src/Header/Server.php b/src/Header/Server.php
index 645c1150ab..b2cc69b752 100644
--- a/src/Header/Server.php
+++ b/src/Header/Server.php
@@ -1,7 +1,7 @@
 <?php
 /**
  * @see       https://github.com/zendframework/zend-http for the canonical source repository
- * @copyright Copyright (c) 2005-2017 Zend Technologies USA Inc. (http://www.zend.com)
+ * @copyright Copyright (c) 2005-2019 Zend Technologies USA Inc. (http://www.zend.com)
  * @license   https://github.com/zendframework/zend-http/blob/master/LICENSE.md New BSD License
  */
 
@@ -28,14 +28,12 @@ public static function fromString($headerLine)
         }
 
         // @todo implementation details
-        $header = new static($value);
-
-        return $header;
+        return new static($value);
     }
 
     public function __construct($value = null)
     {
-        if ($value) {
+        if ($value !== null) {
             HeaderValue::assertValid($value);
             $this->value = $value;
         }
@@ -48,7 +46,7 @@ public function getFieldName()
 
     public function getFieldValue()
     {
-        return $this->value;
+        return (string) $this->value;
     }
 
     public function toString()
diff --git a/src/Header/TE.php b/src/Header/TE.php
index 0151f741f6..4e05625547 100644
--- a/src/Header/TE.php
+++ b/src/Header/TE.php
@@ -28,14 +28,12 @@ public static function fromString($headerLine)
         }
 
         // @todo implementation details
-        $header = new static($value);
-
-        return $header;
+        return new static($value);
     }
 
     public function __construct($value = null)
     {
-        if ($value) {
+        if ($value !== null) {
             HeaderValue::assertValid($value);
             $this->value = $value;
         }
@@ -48,7 +46,7 @@ public function getFieldName()
 
     public function getFieldValue()
     {
-        return $this->value;
+        return (string) $this->value;
     }
 
     public function toString()
diff --git a/src/Header/Trailer.php b/src/Header/Trailer.php
index 5e1147bfab..fed56485c8 100644
--- a/src/Header/Trailer.php
+++ b/src/Header/Trailer.php
@@ -28,14 +28,12 @@ public static function fromString($headerLine)
         }
 
         // @todo implementation details
-        $header = new static($value);
-
-        return $header;
+        return new static($value);
     }
 
     public function __construct($value = null)
     {
-        if ($value) {
+        if ($value !== null) {
             HeaderValue::assertValid($value);
             $this->value = $value;
         }
@@ -48,7 +46,7 @@ public function getFieldName()
 
     public function getFieldValue()
     {
-        return $this->value;
+        return (string) $this->value;
     }
 
     public function toString()
diff --git a/src/Header/TransferEncoding.php b/src/Header/TransferEncoding.php
index b6b830f18b..28f0f0ed89 100644
--- a/src/Header/TransferEncoding.php
+++ b/src/Header/TransferEncoding.php
@@ -30,14 +30,12 @@ public static function fromString($headerLine)
         }
 
         // @todo implementation details
-        $header = new static($value);
-
-        return $header;
+        return new static($value);
     }
 
     public function __construct($value = null)
     {
-        if ($value) {
+        if ($value !== null) {
             HeaderValue::assertValid($value);
             $this->value = $value;
         }
@@ -50,7 +48,7 @@ public function getFieldName()
 
     public function getFieldValue()
     {
-        return $this->value;
+        return (string) $this->value;
     }
 
     public function toString()
diff --git a/src/Header/Upgrade.php b/src/Header/Upgrade.php
index 1f853430ab..a9e03cf93e 100644
--- a/src/Header/Upgrade.php
+++ b/src/Header/Upgrade.php
@@ -28,14 +28,12 @@ public static function fromString($headerLine)
         }
 
         // @todo implementation details
-        $header = new static($value);
-
-        return $header;
+        return new static($value);
     }
 
     public function __construct($value = null)
     {
-        if ($value) {
+        if ($value !== null) {
             HeaderValue::assertValid($value);
             $this->value = $value;
         }
@@ -48,7 +46,7 @@ public function getFieldName()
 
     public function getFieldValue()
     {
-        return $this->value;
+        return (string) $this->value;
     }
 
     public function toString()
diff --git a/src/Header/UserAgent.php b/src/Header/UserAgent.php
index dc2e3efb1d..33f9216d31 100644
--- a/src/Header/UserAgent.php
+++ b/src/Header/UserAgent.php
@@ -28,14 +28,12 @@ public static function fromString($headerLine)
         }
 
         // @todo implementation details
-        $header = new static($value);
-
-        return $header;
+        return new static($value);
     }
 
     public function __construct($value = null)
     {
-        if ($value) {
+        if ($value !== null) {
             HeaderValue::assertValid($value);
             $this->value = $value;
         }
@@ -48,7 +46,7 @@ public function getFieldName()
 
     public function getFieldValue()
     {
-        return $this->value;
+        return (string) $this->value;
     }
 
     public function toString()
diff --git a/src/Header/Vary.php b/src/Header/Vary.php
index 7342e22683..a77ffb2796 100644
--- a/src/Header/Vary.php
+++ b/src/Header/Vary.php
@@ -28,14 +28,12 @@ public static function fromString($headerLine)
         }
 
         // @todo implementation details
-        $header = new static($value);
-
-        return $header;
+        return new static($value);
     }
 
     public function __construct($value = null)
     {
-        if ($value) {
+        if ($value !== null) {
             HeaderValue::assertValid($value);
             $this->value = $value;
         }
@@ -48,7 +46,7 @@ public function getFieldName()
 
     public function getFieldValue()
     {
-        return $this->value;
+        return (string) $this->value;
     }
 
     public function toString()
diff --git a/src/Header/Via.php b/src/Header/Via.php
index 05cd752c07..f38f7df537 100644
--- a/src/Header/Via.php
+++ b/src/Header/Via.php
@@ -28,14 +28,12 @@ public static function fromString($headerLine)
         }
 
         // @todo implementation details
-        $header = new static($value);
-
-        return $header;
+        return new static($value);
     }
 
     public function __construct($value = null)
     {
-        if ($value) {
+        if ($value !== null) {
             HeaderValue::assertValid($value);
             $this->value = $value;
         }
@@ -48,7 +46,7 @@ public function getFieldName()
 
     public function getFieldValue()
     {
-        return $this->value;
+        return (string) $this->value;
     }
 
     public function toString()
diff --git a/src/Header/WWWAuthenticate.php b/src/Header/WWWAuthenticate.php
index ddc5bd656d..a6c016d8d1 100644
--- a/src/Header/WWWAuthenticate.php
+++ b/src/Header/WWWAuthenticate.php
@@ -31,14 +31,12 @@ public static function fromString($headerLine)
         }
 
         // @todo implementation details
-        $header = new static($value);
-
-        return $header;
+        return new static($value);
     }
 
     public function __construct($value = null)
     {
-        if ($value) {
+        if ($value !== null) {
             HeaderValue::assertValid($value);
             $this->value = $value;
         }
@@ -51,7 +49,7 @@ public function getFieldName()
 
     public function getFieldValue()
     {
-        return $this->value;
+        return (string) $this->value;
     }
 
     public function toString()
diff --git a/src/Header/Warning.php b/src/Header/Warning.php
index 65b6cfa0c7..6ad277f19f 100644
--- a/src/Header/Warning.php
+++ b/src/Header/Warning.php
@@ -28,14 +28,12 @@ public static function fromString($headerLine)
         }
 
         // @todo implementation details
-        $header = new static($value);
-
-        return $header;
+        return new static($value);
     }
 
     public function __construct($value = null)
     {
-        if ($value) {
+        if ($value !== null) {
             HeaderValue::assertValid($value);
             $this->value = $value;
         }
@@ -48,7 +46,7 @@ public function getFieldName()
 
     public function getFieldValue()
     {
-        return $this->value;
+        return (string) $this->value;
     }
 
     public function toString()
diff --git a/test/HeaderTest.php b/test/HeaderTest.php
new file mode 100644
index 0000000000..f80a3f8d07
--- /dev/null
+++ b/test/HeaderTest.php
@@ -0,0 +1,159 @@
+<?php
+/**
+ * @see       https://github.com/zendframework/zend-http for the canonical source repository
+ * @copyright Copyright (c) 2019 Zend Technologies USA Inc. (https://www.zend.com)
+ * @license   https://github.com/zendframework/zend-http/blob/master/LICENSE.md New BSD License
+ */
+
+namespace ZendTest\Http;
+
+use PHPUnit\Framework\TestCase;
+use Zend\Http\Exception\InvalidArgumentException;
+use Zend\Http\Header;
+
+class HeaderTest extends TestCase
+{
+    public function header()
+    {
+        // @codingStandardsIgnoreStart
+        yield Header\AcceptRanges::class            => [Header\AcceptRanges::class, 'Accept-Ranges'];
+        yield Header\AuthenticationInfo::class      => [Header\AuthenticationInfo::class, 'Authentication-Info'];
+        yield Header\Authorization::class           => [Header\Authorization::class, 'Authorization'];
+        yield Header\ContentDisposition::class      => [Header\ContentDisposition::class, 'Content-Disposition'];
+        yield Header\ContentEncoding::class         => [Header\ContentEncoding::class, 'Content-Encoding'];
+        yield Header\ContentLanguage::class         => [Header\ContentLanguage::class, 'Content-Language'];
+        yield Header\ContentLength::class           => [Header\ContentLength::class, 'Content-Length'];
+        yield Header\ContentMD5::class              => [Header\ContentMD5::class, 'Content-MD5'];
+        yield Header\ContentRange::class            => [Header\ContentRange::class, 'Content-Range'];
+        yield Header\ContentTransferEncoding::class => [Header\ContentTransferEncoding::class, 'Content-Transfer-Encoding'];
+        yield Header\ContentType::class             => [Header\ContentType::class, 'Content-Type'];
+        yield Header\Etag::class                    => [Header\Etag::class, 'Etag'];
+        yield Header\Expect::class                  => [Header\Expect::class, 'Expect'];
+        yield Header\From::class                    => [Header\From::class, 'From'];
+        yield Header\Host::class                    => [Header\Host::class, 'Host'];
+        yield Header\IfMatch::class                 => [Header\IfMatch::class, 'If-Match'];
+        yield Header\IfNoneMatch::class             => [Header\IfNoneMatch::class, 'If-None-Match'];
+        yield Header\IfRange::class                 => [Header\IfRange::class, 'If-Range'];
+        yield Header\KeepAlive::class               => [Header\KeepAlive::class, 'Keep-Alive'];
+        yield Header\MaxForwards::class             => [Header\MaxForwards::class, 'Max-Forwards'];
+        yield Header\Origin::class                  => [Header\Origin::class, 'Origin'];
+        yield Header\Pragma::class                  => [Header\Pragma::class, 'Pragma'];
+        yield Header\ProxyAuthenticate::class       => [Header\ProxyAuthenticate::class, 'Proxy-Authenticate'];
+        yield Header\ProxyAuthorization::class      => [Header\ProxyAuthorization::class, 'Proxy-Authorization'];
+        yield Header\Range::class                   => [Header\Range::class, 'Range'];
+        yield Header\Refresh::class                 => [Header\Refresh::class, 'Refresh'];
+        yield Header\Server::class                  => [Header\Server::class, 'Server'];
+        yield Header\TE::class                      => [Header\TE::class, 'TE'];
+        yield Header\Trailer::class                 => [Header\Trailer::class, 'Trailer'];
+        yield Header\TransferEncoding::class        => [Header\TransferEncoding::class, 'Transfer-Encoding'];
+        yield Header\Upgrade::class                 => [Header\Upgrade::class, 'Upgrade'];
+        yield Header\UserAgent::class               => [Header\UserAgent::class, 'User-Agent'];
+        yield Header\Vary::class                    => [Header\Vary::class, 'Vary'];
+        yield Header\Via::class                     => [Header\Via::class, 'Via'];
+        yield Header\Warning::class                 => [Header\Warning::class, 'Warning'];
+        yield Header\WWWAuthenticate::class         => [Header\WWWAuthenticate::class, 'WWW-Authenticate'];
+        // @codingStandardsIgnoreEnd
+    }
+
+    /**
+     * @dataProvider header
+     *
+     * @param string $class
+     * @param string $name
+     */
+    public function testThrowsExceptionIfInvalidHeaderLine($class, $name)
+    {
+        $this->expectException(InvalidArgumentException::class);
+        $this->expectExceptionMessage('Invalid header line for ' . $name . ' string');
+        $class::fromString($name . '-Foo: bar');
+    }
+
+    /**
+     * @dataProvider header
+     *
+     * @param string $class
+     * @param string $name
+     */
+    public function testCaseInsensitiveHeaderName($class, $name)
+    {
+        $header1 = $class::fromString(strtoupper($name) . ': foo');
+        self::assertSame('foo', $header1->getFieldValue());
+
+        $header2 = $class::fromString(strtolower($name) . ': bar');
+        self::assertSame('bar', $header2->getFieldValue());
+    }
+
+    /**
+     * @dataProvider header
+     *
+     * @param string $class
+     * @param string $name
+     */
+    public function testDefaultValues($class, $name)
+    {
+        $header = new $class();
+
+        self::assertSame('', $header->getFieldValue());
+        self::assertSame($name, $header->getFieldName());
+        self::assertSame($name . ': ', $header->toString());
+    }
+
+    /**
+     * @dataProvider header
+     *
+     * @param string $class
+     * @param string $name
+     */
+    public function testSetValueViaConstructor($class, $name)
+    {
+        $header = new $class('foo-bar');
+
+        self::assertSame('foo-bar', $header->getFieldValue());
+        self::assertSame($name . ': foo-bar', $header->toString());
+    }
+
+    /**
+     * @dataProvider header
+     *
+     * @param string $class
+     * @param string $name
+     *
+     * Note: in theory this is invalid, as we would expect value to be string|null.
+     * Null is default value but it is converted to string.
+     */
+    public function testSetIntValueViaConstructor($class, $name)
+    {
+        $header = new $class(100);
+
+        self::assertSame('100', $header->getFieldValue());
+        self::assertSame($name . ': 100', $header->toString());
+    }
+
+    /**
+     * @dataProvider header
+     *
+     * @param string $class
+     * @param string $name
+     */
+    public function testSetZeroStringValueViaConstructor($class, $name)
+    {
+        $header = new $class('0');
+
+        self::assertSame('0', $header->getFieldValue());
+        self::assertSame($name . ': 0', $header->toString());
+    }
+
+    /**
+     * @dataProvider header
+     *
+     * @param string $class
+     * @param string $name
+     */
+    public function testFromStringWithNumber($class, $name)
+    {
+        $header = $class::fromString($name . ': 100');
+
+        self::assertSame('100', $header->getFieldValue());
+        self::assertSame($name . ': 100', $header->toString());
+    }
+}