diff --git a/Modules/Compiler/Clang.cmake b/Modules/Compiler/Clang.cmake
index 9f900df31f..5862521cfc 100644
--- a/Modules/Compiler/Clang.cmake
+++ b/Modules/Compiler/Clang.cmake
@@ -19,7 +19,6 @@ if("x${CMAKE_C_SIMULATE_ID}" STREQUAL "xMSVC"
     OR "x${CMAKE_CXX_SIMULATE_ID}" STREQUAL "xMSVC"
     OR "x${CMAKE_Fortran_SIMULATE_ID}" STREQUAL "xMSVC")
   macro(__compiler_clang lang)
-    set(CMAKE_INCLUDE_SYSTEM_FLAG_${lang} "-imsvc ")
   endmacro()
 else()
   include(Compiler/GNU)
diff --git a/Modules/Platform/Windows-Clang.cmake b/Modules/Platform/Windows-Clang.cmake
index dc41572121..c508ac1a59 100644
--- a/Modules/Platform/Windows-Clang.cmake
+++ b/Modules/Platform/Windows-Clang.cmake
@@ -174,6 +174,7 @@ if("x${CMAKE_C_SIMULATE_ID}" STREQUAL "xMSVC"
     macro(__windows_compiler_clang_base lang)
       set(_COMPILE_${lang} "${_COMPILE_${lang}_MSVC}")
       __windows_compiler_msvc(${lang})
+      set(CMAKE_INCLUDE_SYSTEM_FLAG_${lang} "-imsvc ")
     endmacro()
   else()
     cmake_policy(GET CMP0091 __WINDOWS_CLANG_CMP0091)