diff --git a/google/refine/refine.py b/google/refine/refine.py
index 13a70af..a86d250 100644
--- a/google/refine/refine.py
+++ b/google/refine/refine.py
@@ -221,7 +221,11 @@ class RefineProject:
         if not isinstance(server, RefineServer):
             if '/project?project=' in server:
                 server, project_id = server.split('/project?project=')
-            server = RefineServer(server)
+                server = RefineServer(server)
+            elif re.match(r'\d+$', server):     # just digits => project ID
+                server, project_id = RefineServer(), server
+            else:
+                server = RefineServer(server)
         self.server = server
         if not project_id:
             raise Exception('Missing Refine project ID')
diff --git a/tests/test_refine_small.py b/tests/test_refine_small.py
index d263eb0..bb459e6 100644
--- a/tests/test_refine_small.py
+++ b/tests/test_refine_small.py
@@ -63,6 +63,9 @@ class RefineProjectTest(unittest.TestCase):
         p = RP('http://server/varnish/project?project=1658955153749')
         self.assertEqual(p.server.server, 'http://server/varnish')
         self.assertEqual(p.project_id, '1658955153749')
+        p = RP('1658955153749')
+        self.assertEqual(p.server.server, 'http://127.0.0.1:3333')
+        self.assertEqual(p.project_id, '1658955153749')
 
     def tearDown(self):
         # Restore mocked get_models