diff --git a/flask_socketio/__init__.py b/flask_socketio/__init__.py
index 932428ac..0977c828 100644
--- a/flask_socketio/__init__.py
+++ b/flask_socketio/__init__.py
@@ -21,6 +21,8 @@ def __init__(self, app, socket):
     def __call__(self, environ, start_response):
         path = environ['PATH_INFO'].strip('/')
         if path is not None and path.startswith('socket.io'):
+            if 'socketio' not in environ:
+                raise RuntimeError('You need to use a gevent-socketio server.')
             socketio_manage(environ, self.socket.get_namespaces(), self.app,
                             json_loads=json.loads, json_dumps=json.dumps)
         else: