diff --git a/Tests/AbstractWebApplicationTest.php b/Tests/AbstractWebApplicationTest.php
index 5e478b11..34aea9d8 100644
--- a/Tests/AbstractWebApplicationTest.php
+++ b/Tests/AbstractWebApplicationTest.php
@@ -263,7 +263,8 @@ public function testCompressWithGzipEncoding()
 		$this->assertSame(
 			array(
 				0 => array('name' => 'Content-Encoding', 'value' => 'gzip'),
-				1 => array('name' => 'X-Content-Encoded-By', 'value' => 'Joomla')
+				1 => array('name' => 'Vary', 'value' => 'Accept-Encoding'),
+				2 => array('name' => 'X-Content-Encoded-By', 'value' => 'Joomla')
 			),
 			$object->getHeaders()
 		);
@@ -327,7 +328,8 @@ public function testCompressWithDeflateEncoding()
 		$this->assertSame(
 			array(
 				0 => array('name' => 'Content-Encoding', 'value' => 'deflate'),
-				1 => array('name' => 'X-Content-Encoded-By', 'value' => 'Joomla')
+				1 => array('name' => 'Vary', 'value' => 'Accept-Encoding'),
+				2 => array('name' => 'X-Content-Encoded-By', 'value' => 'Joomla')
 			),
 			$object->getHeaders()
 		);
diff --git a/src/AbstractWebApplication.php b/src/AbstractWebApplication.php
index aba1366e..7d28fccc 100644
--- a/src/AbstractWebApplication.php
+++ b/src/AbstractWebApplication.php
@@ -270,6 +270,7 @@ protected function compress()
 
 				// Set the encoding headers.
 				$this->setHeader('Content-Encoding', $encoding);
+				$this->setHeader('Vary', 'Accept-Encoding');
 				$this->setHeader('X-Content-Encoded-By', 'Joomla');
 
 				// Replace the output with the encoded data.