diff --git a/socketio/base_manager.py b/socketio/base_manager.py
index c8e6ff3..7d13f1f 100644
--- a/socketio/base_manager.py
+++ b/socketio/base_manager.py
@@ -94,7 +94,7 @@ class BaseManager(object):
         for sid in self.get_participants(namespace, room):
             if sid != skip_sid:
                 if callback is not None:
-                    id = self.server._generate_ack_id(sid, namespace, callback)
+                    id = self._generate_ack_id(sid, namespace, callback)
                 else:
                     id = None
                 self.server._emit_internal(sid, event, data, namespace, id)
diff --git a/tests/test_base_manager.py b/tests/test_base_manager.py
index 9790777..1cdfa6b 100644
--- a/tests/test_base_manager.py
+++ b/tests/test_base_manager.py
@@ -220,9 +220,11 @@ class TestBaseManager(unittest.TestCase):
 
     def test_emit_with_callback(self):
         self.bm.connect('123', '/foo')
-        self.bm.server._generate_ack_id.return_value = 11
+        self.bm._generate_ack_id = mock.MagicMock()
+        self.bm._generate_ack_id.return_value = 11
         self.bm.emit('my event', {'foo': 'bar'}, namespace='/foo',
                      callback='cb')
+        self.bm._generate_ack_id.assert_called_once_with('123', '/foo', 'cb')
         self.bm.server._emit_internal.assert_called_once_with('123',
                                                               'my event',
                                                               {'foo': 'bar'},