diff --git a/grammar/src/lexical.grm b/grammar/src/lexical.grm
index 494b58f2564..2da24ec5200 100644
--- a/grammar/src/lexical.grm
+++ b/grammar/src/lexical.grm
@@ -46,7 +46,6 @@ new
 true
 false
 is
-isnot
 in
 throw
 return