diff --git a/src/compiler/types.ts b/src/compiler/types.ts
index 14b80325aa3..aefcce6d0bb 100644
--- a/src/compiler/types.ts
+++ b/src/compiler/types.ts
@@ -4339,7 +4339,7 @@ namespace ts {
      */
     export type Visitor = (node: Node) => VisitResult<Node>;
 
-    export type VisitResult<T extends Node> = T | T[];
+    export type VisitResult<T extends Node> = T | T[] | undefined;
 
     export interface Printer {
         /**