diff --git a/index.js b/index.js
index 1f21ae0..f6c279e 100644
--- a/index.js
+++ b/index.js
@@ -17,7 +17,9 @@ const drawCanvas = function() {
       return;
     }
 
-    event.target.classList.add(brushClass);
+    if (brushClass) {
+      event.target.classList.add(brushClass);
+    }
   });
 }