diff --git a/src/services/types.ts b/src/services/types.ts
index 846242b3cf3cc..bb5a588bfc480 100644
--- a/src/services/types.ts
+++ b/src/services/types.ts
@@ -182,6 +182,7 @@ namespace ts {
         isCancellationRequested(): boolean;
     }
 
+    /*@internal*/
     export interface CancellationToken {
         throwIfCancellationRequested(cleanup?: () => void): void;
     }