diff --git a/srcs/cmake/tests.cmake b/srcs/cmake/tests.cmake
index 18f5bf21e..526677527 100644
--- a/srcs/cmake/tests.cmake
+++ b/srcs/cmake/tests.cmake
@@ -23,6 +23,7 @@ IF(KUNGFU_BUILD_GTEST)
     EXTERNALPROJECT_ADD(
         libgtest-dev-repo
         GIT_REPOSITORY ${GTEST_GIT_URL}
+        GIT_TAG main
         PREFIX ${PREFIX}
         CMAKE_ARGS -DCMAKE_INSTALL_PREFIX=${PREFIX}
                    -DCMAKE_CXX_FLAGS=-std=c++11 -Dgtest_disable_pthreads=1
diff --git a/srcs/python/kungfu/tensorflow/optimizers/core.py b/srcs/python/kungfu/tensorflow/optimizers/core.py
index 6ccd4441c..339852bd2 100644
--- a/srcs/python/kungfu/tensorflow/optimizers/core.py
+++ b/srcs/python/kungfu/tensorflow/optimizers/core.py
@@ -38,7 +38,7 @@ def apply_gradients(self, grads_and_vars, **kwargs):
                                           grads_and_vars, **kwargs)
 
     def get_config(self):
-        return self._optimizer.optimizer.get_config()
+        return self._optimizer.get_config()
 
 
 class _KungFuAlgorithm: