diff --git a/tools/broccoli/broccoli-dest-copy.ts b/tools/broccoli/broccoli-dest-copy.ts
index 87152ea7a7..b52777e4e1 100644
--- a/tools/broccoli/broccoli-dest-copy.ts
+++ b/tools/broccoli/broccoli-dest-copy.ts
@@ -35,13 +35,13 @@ class DestCopy implements DiffingBroccoliPlugin {
     // Write log of added/changed/removed files to be used when we call `karma run` from gulp.
     var karmaArgs = '';
     if (treeDiff.addedPaths.length) {
-      karmaArgs +=  ' --addedFiles ' + treeDiff.addedPaths.join(',');
+      karmaArgs += ' --addedFiles ' + treeDiff.addedPaths.join(',');
     }
     if (treeDiff.changedPaths.length) {
-      karmaArgs +=  ' --changedFiles ' + treeDiff.changedPaths.join(',');
+      karmaArgs += ' --changedFiles ' + treeDiff.changedPaths.join(',');
     }
     if (treeDiff.removedPaths.length) {
-      karmaArgs +=  ' --removedFiles ' + treeDiff.removedPaths.join(',')
+      karmaArgs += ' --removedFiles ' + treeDiff.removedPaths.join(',')
     }
     fs.writeFileSync(path.join('tmp', 'build-log-karma-args.txt'), karmaArgs, {encoding: 'utf-8'});
   }