diff --git a/src/compiler/types.ts b/src/compiler/types.ts
index 7cc8dcd81d2..224c26a7263 100644
--- a/src/compiler/types.ts
+++ b/src/compiler/types.ts
@@ -1020,6 +1020,7 @@ namespace ts {
         | SyntaxKind.ExclamationEqualsEqualsToken
         | SyntaxKind.ExclamationEqualsToken
         | SyntaxKind.InstanceOfKeyword
+        | SyntaxKind.InKeyword
         | SyntaxKind.CommaToken;
 
     export type BinaryOperatorToken = Token<BinaryOperator>;