diff --git a/autobahn/asyncio/test/test_asyncio_websocket.py b/autobahn/asyncio/test/test_asyncio_websocket.py
index a752d3bb..d5525f2b 100644
--- a/autobahn/asyncio/test/test_asyncio_websocket.py
+++ b/autobahn/asyncio/test/test_asyncio_websocket.py
@@ -32,3 +32,41 @@ class Test(TestCase):
         transport = Mock()
 
         server.connection_made(transport)
+
+    def test_async_on_connect_server(self):
+        # see also issue 757
+
+        async def foo(x):
+            return x * x
+
+        values = []
+        async def on_connect(req):
+            x = await foo(42)
+            values.append(x)
+
+        factory = WebSocketServerFactory()
+        server = factory()
+        server.onConnect = on_connect
+        transport = Mock()
+
+        server.connection_made(transport)
+        # need/want to insert real-fake handshake data?
+        server.data = b"\r\n".join([
+            b'GET /ws HTTP/1.1',
+            b'Host: www.example.com',
+            b'Sec-WebSocket-Version: 13',
+            b'Origin: http://www.example.com.malicious.com',
+            b'Sec-WebSocket-Extensions: permessage-deflate',
+            b'Sec-WebSocket-Key: tXAxWFUqnhi86Ajj7dRY5g==',
+            b'Connection: keep-alive, Upgrade',
+            b'Upgrade: websocket',
+            b'\r\n',  # last string doesn't get a \r\n from join()
+        ])
+        server.processHandshake()
+
+        import asyncio
+        from asyncio.test_utils import run_once
+        run_once(asyncio.get_event_loop())
+
+        self.assertEqual(1, len(values))
+        self.assertEqual(42 * 42, values[0])
diff --git a/autobahn/asyncio/websocket.py b/autobahn/asyncio/websocket.py
index f08ac6d9..944f4fe4 100644
--- a/autobahn/asyncio/websocket.py
+++ b/autobahn/asyncio/websocket.py
@@ -202,14 +202,19 @@ class WebSocketServerProtocol(WebSocketAdapterProtocol, protocol.WebSocketServer
         # noinspection PyBroadException
         try:
             res = self.onConnect(request)
-            if yields(res):
-                asyncio.async(res)
         except ConnectionDeny as e:
             self.failHandshake(e.reason, e.code)
         except Exception as e:
             self.failHandshake("Internal server error: {}".format(e), ConnectionDeny.INTERNAL_SERVER_ERROR)
         else:
-            self.succeedHandshake(res)
+            if yields(res):
+                # if onConnect was an async method, we need to await
+                # the actual result before calling succeedHandshake
+                asyncio.async(res).add_done_callback(
+                    lambda res: self.succeedHandshake(res.result())
+                )
+            else:
+                self.succeedHandshake(res)
 
 
 class WebSocketClientProtocol(WebSocketAdapterProtocol, protocol.WebSocketClientProtocol):