diff --git a/fileformats.yml b/fileformats.yml
index 6500c55..eac8e62 100644
--- a/fileformats.yml
+++ b/fileformats.yml
@@ -1058,6 +1058,7 @@ fmt/199:
         - mp4
   rename:
     new_name: "{name}.mp4"
+    on_extension_mismatch: true
 fmt/206:
   name: Structured Query Language Data
   action: convert