diff --git a/addon/-private/router-ext.js b/addon/-private/router-ext.js
index <HASH>..<HASH> 100644
--- a/addon/-private/router-ext.js
+++ b/addon/-private/router-ext.js
@@ -251,8 +251,11 @@ Router.reopen({
       mountPoint
     });
 
-    engineInstance.boot();
+    engineInstances[name][instanceId] = engineInstance;
 
-    return engineInstances[name][instanceId] = engineInstance;
+    return engineInstance.boot()
+      .then(() => {
+        return engineInstance;
+      });
   }
 });
Ensure the engine instances promise properly rejects if boot fails.