diff --git a/src/media.cls.php b/src/media.cls.php
index 6e5f185c5..122c74863 100644
--- a/src/media.cls.php
+++ b/src/media.cls.php
@@ -482,7 +482,7 @@ public function webp_support()
 				}
 			}
 
-			if (preg_match('/Firefox\/(\d+)/iU', $_SERVER['HTTP_USER_AGENT'], $matches)) { // TODO: Test if needs `/U`
+			if (preg_match('/Firefox\/(\d+)/i', $_SERVER['HTTP_USER_AGENT'], $matches)) {
 				if ($matches[1] >= 65) {
 					return true;
 				}