diff --git a/lib/queue.js b/lib/queue.js
index 04420c4d0..9809d2a6a 100755
--- a/lib/queue.js
+++ b/lib/queue.js
@@ -663,8 +663,10 @@ Queue.prototype.setHandler = function(name, handler) {
   this.setWorkerName();
 
   if (typeof handler === 'string') {
+    const supportedFileTypes = ['js', 'ts', 'flow'];
     const processorFile =
-      handler + (path.extname(handler) === '.js' ? '' : '.js');
+      handler +
+      (supportedFileTypes.indexOf(path.extname(handler)) !== '-1' ? '' : '.js');
 
     if (!fs.existsSync(processorFile)) {
       throw new Error('File ' + processorFile + ' does not exist');