diff --git a/lib/redmine_dmsf/patches/attachable_patch.rb b/lib/redmine_dmsf/patches/attachable_patch.rb
index 44da87fd..bdc4867e 100644
--- a/lib/redmine_dmsf/patches/attachable_patch.rb
+++ b/lib/redmine_dmsf/patches/attachable_patch.rb
@@ -31,7 +31,7 @@ module RedmineDmsf
       module InstanceMethods
 
         def has_attachments_with_has_attachments_dms?
-          has_attachments_without_has_attachments_dms? || self.dmsf_files.any?
+          has_attachments_without_has_attachments_dms? || (defined?(self.dmsf_files) && self.dmsf_files.any?)
         end
 
       end