diff --git a/utils/bazel/llvm-project-overlay/llvm/config.bzl b/utils/bazel/llvm-project-overlay/llvm/config.bzl
--- a/utils/bazel/llvm-project-overlay/llvm/config.bzl
+++ b/utils/bazel/llvm-project-overlay/llvm/config.bzl
@@ -71,7 +71,7 @@
     # LLVM features
     r'LTDL_SHLIB_EXT=\".dll\"',
     r'LLVM_PLUGIN_EXT=\".dll\"',
-    "LLVM_WINDOWS_PREFER_FORWARD_SLASH=1",
+    "LLVM_WINDOWS_PREFER_FORWARD_SLASH=0",
 ]
 
 # TODO: We should switch to platforms-based config settings to make this easier