diff --git a/libcxx/CMakeLists.txt b/libcxx/CMakeLists.txt
index 1d4375d30ae0..15b76d224e6b 100644
--- a/libcxx/CMakeLists.txt
+++ b/libcxx/CMakeLists.txt
@@ -185,7 +185,9 @@ macro(append_if list condition var)
 endmacro()
 
 # Get warning flags
-append_if(LIBCXX_CXX_WARNING_FLAGS LIBCXX_HAS_WALL_FLAG -Wall)
+if (NOT MSVC)
+  append_if(LIBCXX_CXX_WARNING_FLAGS LIBCXX_HAS_WALL_FLAG -Wall)
+endif()
 append_if(LIBCXX_CXX_WARNING_FLAGS LIBCXX_HAS_W_FLAG -W)
 append_if(LIBCXX_CXX_WARNING_FLAGS LIBCXX_HAS_WNO_UNUSED_PARAMETER_FLAG -Wno-unused-parameter)
 append_if(LIBCXX_CXX_WARNING_FLAGS LIBCXX_HAS_WWRITE_STRINGS_FLAG -Wwrite-strings)