diff --git a/src/Uri.php b/src/Uri.php
index 423eda6bd..db3a1df9f 100644
--- a/src/Uri.php
+++ b/src/Uri.php
@@ -745,6 +745,10 @@ public function setHost($host)
             ), Exception\InvalidUriPartException::INVALID_HOSTNAME);
         }
 
+        if ($host !== null) {
+            $host = strtolower($host);
+        }
+
         $this->host = $host;
         return $this;
     }
diff --git a/test/UriTest.php b/test/UriTest.php
index 1db42d10d..16064bf15 100644
--- a/test/UriTest.php
+++ b/test/UriTest.php
@@ -309,7 +309,7 @@ public function testSetGetValidHost($host)
     {
         $uri = new Uri;
         $uri->setHost($host);
-        $this->assertEquals($host, $uri->getHost());
+        $this->assertEquals(strtolower($host), $uri->getHost());
     }
 
     /**
@@ -821,12 +821,12 @@ public function validUriStringProvider()
             ['mailto:bob@example.com'],
             ['bob@example.com'],
             ['http://a_.!~*\'(-)n0123Di%25%26:pass;:&=+$,word@www.zend.com'],
-            ['http://[FEDC:BA98:7654:3210:FEDC:BA98:7654:3210]:80/index.html'],
-            ['http://[1080::8:800:200C:417A]/foo'],
+            ['http://[fedc:ba98:7654:3210:fedc:ba98:7654:3210]:80/index.html'],
+            ['http://[1080::8:800:200c:417a]/foo'],
             ['http://[::192.9.5.5]/ipng'],
-            ['http://[::FFFF:129.144.52.38]:80/index.html'],
+            ['http://[::ffff:129.144.52.38]:80/index.html'],
             ['http://[2620:0:1cfe:face:b00c::3]/'],
-            ['http://[2010:836B:4179::836B:4179]'],
+            ['http://[2010:836b:4179::836b:4179]'],
             ['http'],
             ['www.example.org:80'],
             ['www.example.org'],