diff --git a/utils/bazel/llvm-project-overlay/llvm/include/llvm/Config/config.h b/utils/bazel/llvm-project-overlay/llvm/include/llvm/Config/config.h
--- a/utils/bazel/llvm-project-overlay/llvm/include/llvm/Config/config.h
+++ b/utils/bazel/llvm-project-overlay/llvm/include/llvm/Config/config.h
@@ -37,7 +37,7 @@
 
 /* Define to 1 to prefer forward slashes on Windows, and to 0 prefer
    backslashes. */
-/* #undef LLVM_WINDOWS_PREFER_FORWARD_SLASH */
+#define LLVM_WINDOWS_PREFER_FORWARD_SLASH 0
 
 /* Define to 1 if you have the `backtrace' function. */
 /* HAVE_BACKTRACE defined in Bazel */