diff --git a/compiler-rt/lib/asan/CMakeLists.txt b/compiler-rt/lib/asan/CMakeLists.txt
--- a/compiler-rt/lib/asan/CMakeLists.txt
+++ b/compiler-rt/lib/asan/CMakeLists.txt
@@ -92,7 +92,7 @@
 
 # Silence warnings in system headers with MSVC.
 if(NOT CLANG_CL)
-  append_list_if(COMPILER_RT_HAS_EXTERNAL_FLAG "/experimental:external /external:W0 /external:anglebrackets" ASAN_CFLAGS)
+  append_list_if(COMPILER_RT_HAS_EXTERNAL_FLAG "/experimental:external;/external:W0;/external:anglebrackets" ASAN_CFLAGS)
 endif()
 
 # Too many existing bugs, needs cleanup.
diff --git a/compiler-rt/lib/interception/CMakeLists.txt b/compiler-rt/lib/interception/CMakeLists.txt
--- a/compiler-rt/lib/interception/CMakeLists.txt
+++ b/compiler-rt/lib/interception/CMakeLists.txt
@@ -21,7 +21,7 @@
 
 # Silence warnings in system headers with MSVC.
 if(NOT CLANG_CL)
-  append_list_if(COMPILER_RT_HAS_EXTERNAL_FLAG "/experimental:external /external:W0 /external:anglebrackets" INTERCEPTION_CFLAGS)
+  append_list_if(COMPILER_RT_HAS_EXTERNAL_FLAG "/experimental:external;/external:W0;/external:anglebrackets" INTERCEPTION_CFLAGS)
 endif()
 
 add_compiler_rt_object_libraries(RTInterception
diff --git a/compiler-rt/lib/ubsan/CMakeLists.txt b/compiler-rt/lib/ubsan/CMakeLists.txt
--- a/compiler-rt/lib/ubsan/CMakeLists.txt
+++ b/compiler-rt/lib/ubsan/CMakeLists.txt
@@ -57,7 +57,7 @@
 
 # Silence warnings in system headers with MSVC.
 if(NOT CLANG_CL)
-  append_list_if(COMPILER_RT_HAS_EXTERNAL_FLAG "/experimental:external /external:W0 /external:anglebrackets" UBSAN_CXXFLAGS)
+  append_list_if(COMPILER_RT_HAS_EXTERNAL_FLAG "/experimental:external;/external:W0;/external:anglebrackets" UBSAN_CXXFLAGS)
 endif()
 
 set(UBSAN_LINK_FLAGS ${SANITIZER_COMMON_LINK_FLAGS})