diff --git a/models/errors.tsp b/models/errors.tsp
index cb0a6ec..f34443c 100644
--- a/models/errors.tsp
+++ b/models/errors.tsp
@@ -1,5 +1,6 @@
 enum ErrorCode {
   FORM_NOT_FOUND,
+  ANSWER_NOT_FOUND,
   OUT_OF_PERIOD,
   DO_NOT_HAVE_PERMISSION_TO_POST_FORM_COMMENT,
   INTERNAL_SERVER_ERROR,