diff --git a/hydrus/core/HydrusConstants.py b/hydrus/core/HydrusConstants.py
index 3bf7a93d..64aa3bbc 100644
--- a/hydrus/core/HydrusConstants.py
+++ b/hydrus/core/HydrusConstants.py
@@ -1121,12 +1121,12 @@ mime_ext_lookup = {
     IMAGE_TIFF : '.tiff',
     IMAGE_ICON : '.ico',
     IMAGE_SVG : '.svg',
-    IMAGE_HEIF: 'heif',
-    IMAGE_HEIF_SEQUENCE: 'heifs',
-    IMAGE_HEIC: 'heic',
-    IMAGE_HEIC_SEQUENCE: 'heics',
-    IMAGE_AVIF: 'avif',
-    IMAGE_AVIF_SEQUENCE: 'avifs',
+    IMAGE_HEIF: '.heif',
+    IMAGE_HEIF_SEQUENCE: '.heifs',
+    IMAGE_HEIC: '.heic',
+    IMAGE_HEIC_SEQUENCE: '.heics',
+    IMAGE_AVIF: '.avif',
+    IMAGE_AVIF_SEQUENCE: '.avifs',
     APPLICATION_FLASH : '.swf',
     APPLICATION_OCTET_STREAM : '.bin',
     APPLICATION_YAML : '.yaml',