diff --git a/api/api.proto b/api/api.proto
index 9a7534cf6..2505fa48d 100644
--- a/api/api.proto
+++ b/api/api.proto
@@ -1051,6 +1051,8 @@ message Return {
     SERVER_BUSY = 9;
     NO_CONNECTION = 10;
     NOT_ENOUGH_EFFECTIVE_CONNECTION = 11;
+    BLOCK_UNSOLIDIFIED = 12;
+
     OTHER_ERROR = 20;
   }