diff --git a/cmake/modules/HandleLLVMOptions.cmake b/cmake/modules/HandleLLVMOptions.cmake
index 19e02121b5..e80baec0d2 100644
--- a/cmake/modules/HandleLLVMOptions.cmake
+++ b/cmake/modules/HandleLLVMOptions.cmake
@@ -390,7 +390,7 @@ if( MSVC )
       append("-Wmissing-field-initializers" CMAKE_C_FLAGS CMAKE_CXX_FLAGS)
 
       # enable warnings explicitly.
-      append("-Wnonportable-include-path -Wunused-function" CMAKE_C_FLAGS CMAKE_CXX_FLAGS)
+      append("-Wnonportable-include-path -Wno-unused-function" CMAKE_C_FLAGS CMAKE_CXX_FLAGS)
       append("-Wtrigraphs -Wconstant-logical-operand -Wunused-variable" CMAKE_C_FLAGS CMAKE_CXX_FLAGS)
     endif (CLANG_CL)
   endif (LLVM_ENABLE_WARNINGS)