diff --git a/toolchain/BUILD.bazel b/toolchain/BUILD.bazel
index fa00156236..bf0ee9d368 100644
--- a/toolchain/BUILD.bazel
+++ b/toolchain/BUILD.bazel
@@ -222,11 +222,16 @@ cc_args_list(
 
 # TODO(cerisier): extract those into proper semantic args list.
 # TODO(zbarsky): This must match llvm/toolchains/llvm.bzl
+_DEFAULT_LIBCXX_HEADER_ARGS = select({
+    "@@//third_party/v8:use_rusty_v8_custom_libcxx": [],
+    "//conditions:default": [
+        "//toolchain/args:libcxx_headers_include_search_paths",
+    ],
+})
+
 cc_args_list(
     name = "linux_toolchain_args",
-    args = [
-        "//toolchain/args:libcxx_headers_include_search_paths",
-    ] + select({
+    args = _DEFAULT_LIBCXX_HEADER_ARGS + select({
         "//platforms/config:musl": [
             "//toolchain/args/linux:kernel_headers_include_search_paths",
             "//toolchain/args/linux:musl_libc_headers_include_search_paths",
@@ -252,8 +257,7 @@ cc_args_list(
 # TODO(zbarsky): This must match llvm/toolchains/llvm.bzl
 cc_args_list(
     name = "windows_toolchain_args",
-    args = [
-        "//toolchain/args:libcxx_headers_include_search_paths",
+    args = _DEFAULT_LIBCXX_HEADER_ARGS + [
         "//toolchain/args/windows:mingw_headers_include_search_paths",
     ],
 )
diff --git a/toolchain/llvm/llvm.bzl b/toolchain/llvm/llvm.bzl
index d36d8b94bd..97aa879d4a 100644
--- a/toolchain/llvm/llvm.bzl
+++ b/toolchain/llvm/llvm.bzl
@@ -186,16 +186,22 @@ def declare_llvm_targets(*, suffix = ""):
         ],
     )
 
+    default_libcxx_target_headers = select({
+        "@@//third_party/v8:use_rusty_v8_custom_libcxx": [],
+        "//conditions:default": [
+            "@llvm//runtimes/libcxx:libcxx_headers_include_search_directory",
+            "@llvm//runtimes/libcxx:libcxxabi_headers_include_search_directory",
+        ],
+    })
+
     # This must match //toolchain:linux_toolchain_args
     include_path(
         name = "linux_target_headers",
         srcs = [
             ":builtin_resource_dir",
-            "@llvm//runtimes/libcxx:libcxx_headers_include_search_directory",
-            "@llvm//runtimes/libcxx:libcxxabi_headers_include_search_directory",
             "@kernel_headers//:kernel_headers_directory",
             "@llvm//sanitizers:sanitizers_headers_include_search_directory",
-        ] + select({
+        ] + default_libcxx_target_headers + select({
             "@llvm//platforms/config:musl": [
                 "@llvm//runtimes/musl:musl_headers_include_search_directory",
             ],
@@ -210,13 +216,11 @@ def declare_llvm_targets(*, suffix = ""):
         name = "windows_target_headers",
         srcs = [
             ":builtin_resource_dir",
-            "@llvm//runtimes/libcxx:libcxx_headers_include_search_directory",
-            "@llvm//runtimes/libcxx:libcxxabi_headers_include_search_directory",
             "@mingw//:mingw_generated_headers_crt_directory",
             "@mingw//:mingw_w64_headers_include_directory",
             "@mingw//:mingw_w64_headers_crt_directory",
             "@mingw//:mingw_w64_winpthreads_include_directory",
-        ],
+        ] + default_libcxx_target_headers,
     )
 
     include_path(