diff --git a/apps/theming/lib/ImageManager.php b/apps/theming/lib/ImageManager.php
index 3fe76899dcd..2b58fa499f4 100644
--- a/apps/theming/lib/ImageManager.php
+++ b/apps/theming/lib/ImageManager.php
@@ -260,6 +260,11 @@ class ImageManager {
 			$supportedFormats[] = 'image/svg';
 		}
 
+		if ($key === 'favicon') {
+			$supportedFormats[] = 'image/x-icon';
+			$supportedFormats[] = 'image/vnd.microsoft.icon';
+		}
+
 		return $supportedFormats;
 	}