diff --git a/lib/annotate/annotate_models.rb b/lib/annotate/annotate_models.rb
index fc503839..5948625d 100644
--- a/lib/annotate/annotate_models.rb
+++ b/lib/annotate/annotate_models.rb
@@ -231,7 +231,7 @@ def get_col_type(col)
         'bigint'
       else
         (col.type || col.sql_type).to_s
-      end
+      end.dup
     end
 
     def index_columns_info(index)