diff --git a/src/init.ts b/src/init.ts
index ba1efb614..d6d89b361 100644
--- a/src/init.ts
+++ b/src/init.ts
@@ -12,3 +12,10 @@ registerViewerAction()
 window.OCA = window.OCA ?? {}
 window.OCA.Viewer = new ViewerService()
 window.OCA.Viewer.version = appVersion
+
+// Eagerly register any handlers queued before the viewer was initialized.
+// This must happen synchronously so that OCA.Viewer.mimetypes is complete
+// before the file action's enabled() callback is evaluated by the files app.
+if (window._oca_viewer_handlers) {
+	window._oca_viewer_handlers.forEach(handler => window.OCA.Viewer.registerHandler(handler))
+}