diff --git a/app/models/concerns/attachmentable.rb b/app/models/concerns/attachmentable.rb
index 24f5968de..7c78bb456 100644
--- a/app/models/concerns/attachmentable.rb
+++ b/app/models/concerns/attachmentable.rb
@@ -60,7 +60,9 @@ module Attachmentable
   end
 
   def calculated_content_type(attachment)
-    Paperclip.run('file', '-b --mime :file', file: attachment.queued_for_write[:original].path).split(/[:;\s]+/).first.chomp
+    content_type = Paperclip.run('file', '-b --mime :file', file: attachment.queued_for_write[:original].path).split(/[:;\s]+/).first.chomp
+    content_type = 'video/mp4' if content_type == 'video/x-m4v'
+    content_type
   rescue Terrapin::CommandLineError
     ''
   end