diff --git a/api/controllers/console/explore/installed_app.py b/api/controllers/console/explore/installed_app.py
index 779d0f0a6f..a951b04fc6 100644
--- a/api/controllers/console/explore/installed_app.py
+++ b/api/controllers/console/explore/installed_app.py
@@ -58,7 +58,8 @@ class InstalledAppsListApi(Resource):
             }
             for installed_app in installed_apps
         ]
-        installed_apps.sort(key=lambda app: (-app['is_pinned'], app['last_used_at']))
+        installed_apps.sort(key=lambda app: (-app['is_pinned'], app['last_used_at']
+                            if app['last_used_at'] is not None else float('inf')))
 
         return {'installed_apps': installed_apps}