diff --git a/libs/core/output.ts b/libs/core/output.ts
index 25521c9d..24a4f955 100644
--- a/libs/core/output.ts
+++ b/libs/core/output.ts
@@ -238,7 +238,7 @@ namespace motors {
          */
         //% blockId=motorPauseUntilRead block="%motor|pause until ready"
         //% group="Motion"
-        pauseUntilReady(timeOut: number = -1) {
+        pauseUntilReady(timeOut?: number) {
             pauseUntil(() => this.isReady(), timeOut);
         }
     }