diff --git a/lib/pmacs_refile/attacher.rb b/lib/pmacs_refile/attacher.rb
index 819cad5..cb21838 100644
--- a/lib/pmacs_refile/attacher.rb
+++ b/lib/pmacs_refile/attacher.rb
@@ -145,7 +145,7 @@ def delete!
     end
 
     def remove?
-      remove and remove != "" and remove !~ /\A0|false$\z/
+      remove and remove != "" and remove.to_s !~ /\A0|false$\z/
     end
 
     def present?
diff --git a/lib/pmacs_refile/backend_macros.rb b/lib/pmacs_refile/backend_macros.rb
index 3e14f45..3cbce85 100644
--- a/lib/pmacs_refile/backend_macros.rb
+++ b/lib/pmacs_refile/backend_macros.rb
@@ -35,7 +35,7 @@ def verify_uploadable(method)
     end
 
     def valid_id?(id)
-      id =~ /\A[a-z0-9]+\z/i
+      id.to_s =~ /\A[a-z0-9]+\z/i
     end
 
     def decode_id(id)