diff --git a/depends/protobuf/CMakeLists.txt b/depends/protobuf/CMakeLists.txt
index b175b7744..9ec13e6ca 100644
--- a/depends/protobuf/CMakeLists.txt
+++ b/depends/protobuf/CMakeLists.txt
@@ -201,7 +201,8 @@ google/protobuf/compiler/zip_writer.cc
 LIST(APPEND LIBPROTOBUF_FULL_SRCS ${LIBPROTOBUF_LITE_SRCS})
 
 IF(CMAKE_COMPILER_IS_GNUCC)
-    SET(CMAKE_CXX_FLAGS_RELWITHDEBINFO "${CMAKE_CXX_FLAGS_RELWITHDEBINFO} -Wno-sign-compare  -Wno-unused-result")
+    SET(CMAKE_CXX_FLAGS_RELWITHDEBINFO "${CMAKE_CXX_FLAGS_RELWITHDEBINFO} -Wno-sign-compare")
+    SET(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Wno-unused-result")
 ENDIF()
 
 INCLUDE_DIRECTORIES(${CMAKE_CURRENT_SOURCE_DIR})