diff --git a/app/models/dmsf_file_revision.rb b/app/models/dmsf_file_revision.rb
index 570c8835..d9aaf19a 100644
--- a/app/models/dmsf_file_revision.rb
+++ b/app/models/dmsf_file_revision.rb
@@ -391,7 +391,7 @@ def workflow_tooltip
   end
 
   def protocol
-    @protocol ||= PROTOCOLS[mime_type.downcase]
+    @protocol ||= PROTOCOLS[mime_type.downcase] if mime_type
     @protocol
   end