diff --git a/llvm/CMakeLists.txt b/llvm/CMakeLists.txt
--- a/llvm/CMakeLists.txt
+++ b/llvm/CMakeLists.txt
@@ -567,7 +567,7 @@
 option (LLVM_VERSION_PRINTER_SHOW_HOST_TARGET_INFO
   "Show target and host info when tools are invoked with --version." ON)
 
-option(LLVM_INTEGRATED_CRT_ALLOC "Replace the Windows CRT allocator with any of {rpmalloc|mimalloc|snmalloc}. Only works with /MT enabled." OFF)
+set(LLVM_INTEGRATED_CRT_ALLOC "" CACHE PATH "Replace the Windows CRT allocator with any of {rpmalloc|mimalloc|snmalloc}. Only works with /MT enabled.")
 if(LLVM_INTEGRATED_CRT_ALLOC)
   if(NOT WIN32)
     message(FATAL_ERROR "LLVM_INTEGRATED_CRT_ALLOC is only supported on Windows.")