diff --git a/boards/models/attachment/viewers.py b/boards/models/attachment/viewers.py
--- a/boards/models/attachment/viewers.py
+++ b/boards/models/attachment/viewers.py
@@ -29,7 +29,7 @@ FILE_TYPES_AUDIO = (
     'audio/ogg',
     'audio/mp3',
     'audio/opus',
-    'audio/flac',
+    'audio/x-flac',
 )
 FILE_TYPES_IMAGE = (
     'image/jpeg',