diff --git a/flask_restplus/namespace.py b/flask_restplus/namespace.py
index 6fbe7be5..83a3bb38 100644
--- a/flask_restplus/namespace.py
+++ b/flask_restplus/namespace.py
@@ -53,6 +53,7 @@ def __init__(self, name, description=None, path=None, decorators=None, validate=
         self.apis = []
         if 'api' in kwargs:
             self.apis.append(kwargs['api'])
+            kwargs['api'].add_namespace(self)
 
     @property
     def path(self):
diff --git a/tests/test_namespace.py b/tests/test_namespace.py
index fbb26778..3c58819b 100644
--- a/tests/test_namespace.py
+++ b/tests/test_namespace.py
@@ -133,3 +133,9 @@ def post(self):
         client.post_json('/apples/validation/', data)
 
         assert Payload.payload == data
+
+    def test_api_namespaces(self, app):
+        api = restplus.Api(app, validate=True)
+        ns1 = Namespace('ns1', api=api)
+
+        assert ns1 in api.namespaces