diff --git a/library/Zend/Http/Header/ContentType.php b/library/Zend/Http/Header/ContentType.php
index 44a61ecd477..df67954956b 100644
--- a/library/Zend/Http/Header/ContentType.php
+++ b/library/Zend/Http/Header/ContentType.php
@@ -248,7 +248,13 @@ protected function assembleValue()
     protected function splitMediaTypesFromString($criteria)
     {
         $mediaTypes = explode(',', $criteria);
-        array_walk($mediaTypes, 'trim');
+        array_walk(
+            $mediaTypes,
+            function (&$value) {
+                $value = trim($value);
+            }
+        );
+
         return $mediaTypes;
     }
 
diff --git a/library/Zend/Mail/Header/AbstractAddressList.php b/library/Zend/Mail/Header/AbstractAddressList.php
index 4ccd38bba3f..87f76c7734c 100644
--- a/library/Zend/Mail/Header/AbstractAddressList.php
+++ b/library/Zend/Mail/Header/AbstractAddressList.php
@@ -58,7 +58,12 @@ public static function fromString($headerLine)
         // split value on ","
         $fieldValue = str_replace(Headers::FOLDING, ' ', $fieldValue);
         $values     = explode(',', $fieldValue);
-        array_walk($values, 'trim');
+        array_walk(
+            $values,
+            function (&$value) {
+                $value = trim($value);
+            }
+        );
 
         $addressList = $header->getAddressList();
         foreach ($values as $address) {