diff --git a/karma.conf.cjs b/karma.conf.cjs
index 284d0e0e04..c4f75f0c23 100644
--- a/karma.conf.cjs
+++ b/karma.conf.cjs
@@ -35,7 +35,7 @@ module.exports = config => {
         ],
       },
       resolve: {
-        extensions: ['.ts', '.js'],
+        extensions: ['.ts'],
       },
       stats: {
           colors: true,
diff --git a/tests/layer_manager.spec.ts b/tests/layer_manager.spec.ts
index 1d09039d16..96696c8643 100644
--- a/tests/layer_manager.spec.ts
+++ b/tests/layer_manager.spec.ts
@@ -1,5 +1,6 @@
 import { AnyModel } from '@anywidget/types';
 import '../js/layer_manager';
+
 import { default as layerManagerRender, LayerManager, LayerManagerModel } from '../js/layer_manager';
 import { FakeAnyModel } from './fake_anywidget';