diff --git a/tests/vty/vty_test.err b/tests/vty/vty_test.err
index 25c94e6..a85b129 100644
--- a/tests/vty/vty_test.err
+++ b/tests/vty/vty_test.err
@@ -1,5 +1,6 @@
 Found duplicate flag letter 'f' in application specific attributes (index 0 vs 3)! Please fix.
 Found duplicate flag letter 'z' in application specific attributes (index 2 vs 4)! Please fix.
+Attribute flag letter 'X' is reserved for libraries! Please fix.
 Got VTY event: 2
 Got VTY event: 2
 Got VTY event: 2