diff --git a/phpBB/includes/functions_download.php b/phpBB/includes/functions_download.php
index 02dea6c113..3be84299f0 100644
--- a/phpBB/includes/functions_download.php
+++ b/phpBB/includes/functions_download.php
@@ -60,13 +60,13 @@ function send_avatar_to_browser($file, $browser)
 			}
 			else
 			{
-				header('Expires: ' . gmdate('D, d M Y H:i:s \G\M\T', time() + 31536000));
+				header('Expires: ' . gmdate('D, d M Y H:i:s', time() + 31536000) . ' GMT');
 			}
 		}
 		else
 		{
 			header('Content-Disposition: inline; ' . header_filename($file));
-			header('Expires: ' . gmdate('D, d M Y H:i:s \G\M\T', time() + 31536000));
+			header('Expires: ' . gmdate('D, d M Y H:i:s', time() + 31536000) . ' GMT');
 		}
 
 		$size = @filesize($file_path);
@@ -421,7 +421,7 @@ function set_modified_headers($stamp, $browser)
 			send_status_line(304, 'Not Modified');
 			// seems that we need those too ... browsers
 			header('Pragma: public');
-			header('Expires: ' . gmdate('D, d M Y H:i:s \G\M\T', time() + 31536000));
+			header('Expires: ' . gmdate('D, d M Y H:i:s', time() + 31536000) . ' GMT');
 			return true;
 		}
 		else