diff --git a/cmake/external_gtest.cmake b/cmake/external_gtest.cmake
index e0e3487d662..4fa342c1e87 100644
--- a/cmake/external_gtest.cmake
+++ b/cmake/external_gtest.cmake
@@ -38,7 +38,7 @@ endif()
 if(LINUX)
     # workaround for compile error
     # related: https://github.com/intel/mkl-dnn/issues/55
-    set(GTEST_CXX_FLAGS -Wno-unused-result ${CMAKE_CXX_FLAGS})
+    set(GTEST_CXX_FLAGS "-Wno-unused-result ${CMAKE_CXX_FLAGS}")
 else()
     set(GTEST_CXX_FLAGS ${CMAKE_CXX_FLAGS})
 endif()