diff --git a/src/js/contentscript.js b/src/js/contentscript.js
index fb5e1932e..3ce10096f 100644
--- a/src/js/contentscript.js
+++ b/src/js/contentscript.js
@@ -362,7 +362,7 @@ vAPI.SafeAnimationFrame = class {
     };
 
     // https://github.com/chrisaljoudi/uBlock/issues/205
-    // Do not handle added node directly from within mutation observer.
+    //   Do not handle added node directly from within mutation observer.
     const observerHandler = function(mutations) {
         let i = mutations.length;
         while ( i-- ) {
@@ -376,7 +376,7 @@ vAPI.SafeAnimationFrame = class {
                 removedNodeLists.push(nodeList);
             }
         }
-        if ( addedNodeLists.length !== 0 || removedNodes ) {
+        if ( addedNodeLists.length !== 0 || removedNodeLists.length !== 0 ) {
             safeObserverHandlerTimer.start(
                 addedNodeLists.length < 100 ? 1 : undefined
             );