diff --git a/cmake/modules/HandleLLVMOptions.cmake b/cmake/modules/HandleLLVMOptions.cmake
index f4f96501eba..27147dcfd29 100644
--- a/cmake/modules/HandleLLVMOptions.cmake
+++ b/cmake/modules/HandleLLVMOptions.cmake
@@ -315,6 +315,13 @@ if( MSVC )
   # Enable warnings
   if (LLVM_ENABLE_WARNINGS)
     append("/W4" msvc_warning_flags)
+    # CMake appends /W3 by default, and having /W3 followed by /W4 will result in 
+    # cl : Command line warning D9025 : overriding '/W3' with '/W4'.  Since this is
+    # a command line warning and not a compiler warning, it cannot be suppressed except
+    # by fixing the command line.
+    string(REGEX REPLACE " /W[0-4]" "" CMAKE_C_FLAGS "${CMAKE_C_FLAGS}")
+    string(REGEX REPLACE " /W[0-4]" "" CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS}")
+
     if (LLVM_ENABLE_PEDANTIC)
       # No MSVC equivalent available
     endif (LLVM_ENABLE_PEDANTIC)