diff --git a/modules/doc/application/controllers/ModuleController.php b/modules/doc/application/controllers/ModuleController.php
index 2939561cf..94bbf9583 100644
--- a/modules/doc/application/controllers/ModuleController.php
+++ b/modules/doc/application/controllers/ModuleController.php
@@ -148,14 +148,14 @@ class ModuleController extends DocController
 
         $imageInfo = new SplFileInfo($imagePath);
 
-        $ETag = md5($imageInfo->getMTime() . $imagePath);
+        $etag = md5($imageInfo->getMTime() . $imagePath);
         $lastModified = gmdate('D, d M Y H:i:s T', $imageInfo->getMTime());
         $match = false;
 
         if (isset($_SERER['HTTP_IF_NONE_MATCH'])) {
             $ifNoneMatch = explode(', ', stripslashes($_SERVER['HTTP_IF_NONE_MATCH']));
             foreach ($ifNoneMatch as $tag) {
-                if ($tag === $ETag) {
+                if ($tag === $etag) {
                     $match = true;
                     break;
                 }
@@ -167,20 +167,16 @@ class ModuleController extends DocController
             }
         }
 
-        $finfo = new finfo();
         $this->getResponse()
-            ->setHeader('ETag', $ETag)
-            ->setHeader('Cache-Control', 'no-transform,public,max-age=3600', true)
-            ->setHeader('Last-Modified', $lastModified, true)
-            // Set additional headers for compatibility reasons (Cache-Control should have precedence) in case
-            // session.cache_limiter is set to no cache
-            ->setHeader('Pragma', 'cache', true)
-            ->setHeader('Expires', gmdate('D, d M Y H:i:s T', time() + 3600), true)
-            ->setHeader('Content-Type', $finfo->file($imagePath, FILEINFO_MIME_TYPE));
+            ->setHeader('ETag', $etag)
+            ->setHeader('Cache-Control', 'no-transform,public,max-age=3600,must-revalidate', true);
 
         if ($match) {
             $this->getResponse()->setHttpResponseCode(304);
         } else {
+            $finfo = new finfo();
+            $this->getResponse()
+                ->setHeader('Content-Type', $finfo->file($imagePath, FILEINFO_MIME_TYPE));
             readfile($imagePath);
         }
     }