diff --git a/compiler-rt/CMakeLists.txt b/compiler-rt/CMakeLists.txt
--- a/compiler-rt/CMakeLists.txt
+++ b/compiler-rt/CMakeLists.txt
@@ -559,7 +559,7 @@
   append_list_if(COMPILER_RT_HAS_NOSTDINCXX_FLAG -nostdinc++ COMPILER_RT_COMMON_CFLAGS)
   append_list_if(COMPILER_RT_HAS_NOSTDLIBXX_FLAG -nostdlib++ COMPILER_RT_COMMON_LINK_FLAGS)
   # Use the in-tree libc++ through explicit include and library paths.
-  set(COMPILER_RT_CXX_CFLAGS "$<$<TARGET_EXISTS:cxx-headers>:-isystem$<JOIN:$<TARGET_PROPERTY:cxx-headers,INTERFACE_INCLUDE_DIRECTORIES>,$<SEMICOLON>-isystem>>")
+  set(COMPILER_RT_CXX_CFLAGS "$<$<TARGET_EXISTS:cxx-headers>:$<IF:$<BOOL:${MSVC}>,/imsvc,-isystem>$<JOIN:$<TARGET_PROPERTY:cxx-headers,INTERFACE_INCLUDE_DIRECTORIES>,$<SEMICOLON>$<IF:$<BOOL:${MSVC}>,/imsvc,-isystem>>>")
   if (COMPILER_RT_STATIC_CXX_LIBRARY)
     set(COMPILER_RT_CXX_LINK_LIBS "$<TARGET_LINKER_FILE:cxx_static>")
   else()
@@ -595,7 +595,7 @@
 
 if (SANITIZER_TEST_CXX_LIBNAME STREQUAL "libc++")
   if (SANITIZER_TEST_CXX_INTREE)
-    list(APPEND SANITIZER_TEST_CXX_CFLAGS "$<$<TARGET_EXISTS:cxx-headers>:-isystem$<JOIN:$<TARGET_PROPERTY:cxx-headers,INTERFACE_INCLUDE_DIRECTORIES>,$<SEMICOLON>-isystem>>")
+    list(APPEND SANITIZER_TEST_CXX_CFLAGS "$<$<TARGET_EXISTS:cxx-headers>:$<IF:$<BOOL:${MSVC}>,/imsvc,-isystem>$<JOIN:$<TARGET_PROPERTY:cxx-headers,INTERFACE_INCLUDE_DIRECTORIES>,$<SEMICOLON>$<IF:$<BOOL:${MSVC}>,/imsvc,-isystem>>>")
     if (SANITIZER_USE_STATIC_TEST_CXX)
       list(APPEND SANITIZER_TEST_CXX_LIBRARIES "$<TARGET_LINKER_FILE:cxx_static>")
     else()