diff --git a/core/server/udp_test.go b/core/server/udp_test.go
index aa78327581..045edbd5fa 100644
--- a/core/server/udp_test.go
+++ b/core/server/udp_test.go
@@ -25,7 +25,7 @@ func TestUDPSessionManager(t *testing.T) {
 		}
 		return m, nil
 	})
-	io.EXPECT().Hook(mock.Anything, mock.Anything).Return(nil, nil)
+	io.EXPECT().Hook(mock.Anything, mock.Anything).Return(nil)
 
 	go sm.Run()