diff --git a/src/index.tsx b/src/index.tsx
index c29bffed..1ec76ccd 100644
--- a/src/index.tsx
+++ b/src/index.tsx
@@ -250,7 +250,7 @@ export function generateTrigger(
     componentWillUnmount() {
       this.clearDelayTimer();
       this.clearOutsideHandler();
-      clearTimeout(this.mouseDownTimeout);
+      if (this.mouseDownTimeout != null) clearTimeout(this.mouseDownTimeout);
     }
 
     onMouseEnter = e => {