diff --git a/examples/dependent-project/src/main.ts b/examples/dependent-project/src/main.ts
index 04835137a1..e348b5f8d5 100644
--- a/examples/dependent-project/src/main.ts
+++ b/examples/dependent-project/src/main.ts
@@ -18,9 +18,11 @@ import {makeExtraKeyBindings} from 'my-neuroglancer-project/extra_key_bindings';
 import {navigateToOrigin} from 'my-neuroglancer-project/navigate_to_origin';
 import {setupDefaultViewer} from 'neuroglancer/ui/default_viewer_setup';
 import {registerActionListener} from 'neuroglancer/util/event_action_map';
+import {makeDefaultViewer} from 'neuroglancer/ui/default_viewer';
 
 window.addEventListener('DOMContentLoaded', () => {
-  const viewer = setupDefaultViewer();
+  let viewer = (<any>window)['viewer'] = makeDefaultViewer();
+  setupDefaultViewer(viewer);
   makeExtraKeyBindings(viewer.inputEventMap);
   registerActionListener(viewer.element, 'navigate-to-origin', () => navigateToOrigin(viewer));
 });
diff --git a/src/main.ts b/src/main.ts
index 5620e498fb..ebbbad1d53 100644
--- a/src/main.ts
+++ b/src/main.ts
@@ -18,7 +18,9 @@
  * @file Main entry point for default neuroglancer viewer.
  */
 import {setupDefaultViewer} from 'neuroglancer/ui/default_viewer_setup';
+import {makeDefaultViewer} from 'neuroglancer/ui/default_viewer';
 
 window.addEventListener('DOMContentLoaded', () => {
-  setupDefaultViewer();
+  let viewer = (<any>window)['viewer'] = makeDefaultViewer();
+  setupDefaultViewer(viewer);
 });
diff --git a/src/neuroglancer/ui/default_viewer_setup.ts b/src/neuroglancer/ui/default_viewer_setup.ts
index b82a1d6870..dfdca8f70a 100644
--- a/src/neuroglancer/ui/default_viewer_setup.ts
+++ b/src/neuroglancer/ui/default_viewer_setup.ts
@@ -17,12 +17,12 @@
 import {StatusMessage} from 'neuroglancer/status';
 import {bindDefaultCopyHandler, bindDefaultPasteHandler} from 'neuroglancer/ui/default_clipboard_handling';
 import {setDefaultInputEventBindings} from 'neuroglancer/ui/default_input_event_bindings';
-import {makeDefaultViewer} from 'neuroglancer/ui/default_viewer';
 import {bindTitle} from 'neuroglancer/ui/title';
 import {UrlHashBinding} from 'neuroglancer/ui/url_hash_binding';
 import {UserLayer, UserLayerConstructor, layerTypes} from 'neuroglancer/layer';
 import {Tool, restoreTool} from 'neuroglancer/ui/tool';
 import {verifyObject, verifyObjectProperty, verifyString} from 'neuroglancer/util/json';
+import {Viewer} from 'neuroglancer/viewer';
 
 declare var NEUROGLANCER_DEFAULT_STATE_FRAGMENT: string|undefined;
 
@@ -40,8 +40,7 @@ export const hasCustomBindings = typeof CUSTOM_BINDINGS !== 'undefined' && Objec
 /**
  * Sets up the default neuroglancer viewer.
  */
-export function setupDefaultViewer() {
-  let viewer = (<any>window)['viewer'] = makeDefaultViewer();
+export function setupDefaultViewer(viewer: Viewer) {
   setDefaultInputEventBindings(viewer.inputEventBindings);
 
   const bindNonLayerSpecificTool = (obj: unknown, toolKey: string, desiredLayerType: UserLayerConstructor, desiredProvider?: string) => {