diff --git a/src/core/lib/iomgr/tcp_client_custom.cc b/src/core/lib/iomgr/tcp_client_custom.cc
index 932c79e..9389861 100644
--- a/src/core/lib/iomgr/tcp_client_custom.cc
+++ b/src/core/lib/iomgr/tcp_client_custom.cc
@@ -140,12 +140,12 @@
             socket, connect->addr_name);
   }
 
-  grpc_custom_socket_vtable->connect(
-      socket, (const grpc_sockaddr*)resolved_addr->addr, resolved_addr->len,
-      custom_connect_callback);
   GRPC_CLOSURE_INIT(&connect->on_alarm, on_alarm, socket,
                     grpc_schedule_on_exec_ctx);
   grpc_timer_init(&connect->alarm, deadline, &connect->on_alarm);
+  grpc_custom_socket_vtable->connect(
+      socket, (const grpc_sockaddr*)resolved_addr->addr, resolved_addr->len,
+      custom_connect_callback);
 }
 
 grpc_tcp_client_vtable custom_tcp_client_vtable = {tcp_connect};
diff --git a/src/python/grpcio/grpc/_cython/_cygrpc/credentials.pyx.pxi b/src/python/grpcio/grpc/_cython/_cygrpc/credentials.pyx.pxi
index 500086f..dff9097 100644
--- a/src/python/grpcio/grpc/_cython/_cygrpc/credentials.pyx.pxi
+++ b/src/python/grpcio/grpc/_cython/_cygrpc/credentials.pyx.pxi
@@ -17,6 +17,17 @@
 import grpc
 import threading
 
+def _spawn_callback_in_thread(cb_func, args):
+  threading.Thread(target=cb_func, args=args).start()
+
+async_callback_func = _spawn_callback_in_thread
+
+def set_async_callback_func(callback_func):
+  global async_callback_func
+  async_callback_func = callback_func
+
+def _spawn_callback_async(callback, args):
+  async_callback_func(callback, args)
 
 cdef class CallCredentials:
 
@@ -40,7 +51,7 @@
     else:
       cb(user_data, NULL, 0, status, error_details)
   args = context.service_url, context.method_name, callback,
-  threading.Thread(target=<object>state, args=args).start()
+  _spawn_callback_async(<object>state, args)
   return 0  # Asynchronous return
 
 
diff --git a/src/python/grpcio/grpc/_cython/_cygrpc/grpc_gevent.pyx b/src/python/grpcio/grpc/_cython/_cygrpc/grpc_gevent.pyx
index 31ef671..f9a1b28 100644
--- a/src/python/grpcio/grpc/_cython/_cygrpc/grpc_gevent.pyx
+++ b/src/python/grpcio/grpc/_cython/_cygrpc/grpc_gevent.pyx
@@ -418,6 +418,11 @@
 
   g_event = gevent.event.Event()
   g_pool = gevent.pool.Group()
+
+  def cb_func(cb, args):
+    _spawn_greenlet(cb, *args)
+  set_async_callback_func(cb_func)
+
   gevent_resolver_vtable.resolve = socket_resolve
   gevent_resolver_vtable.resolve_async = socket_resolve_async