diff --git a/.github/workflows/build.yml b/.github/workflows/build.yml
index d785c7a..2191181 100644
--- a/.github/workflows/build.yml
+++ b/.github/workflows/build.yml
@@ -266,7 +266,7 @@ jobs:
           ./build-all.sh $(pwd)/install/llvm-mingw --disable-clang-tools-extra --disable-lldb $ARGS
           .github/workflows/store-version.sh install/llvm-mingw/versions.txt
           ./copy-msys-dependencies.sh $(pwd)/install/llvm-mingw ${{matrix.sys}}
-          NATIVE=1 ./test-libcxx-module.sh $(pwd)/install/llvm-mingw
+          ./test-libcxx-module.sh $(pwd)/install/llvm-mingw
           ./run-tests.sh $(pwd)/install/llvm-mingw
           cd install
           NAME=llvm-mingw-$TAG-ucrt-msys2-${{matrix.sys}}
@@ -362,7 +362,7 @@ jobs:
       - uses: actions/checkout@v4
       - name: Run tests
         run: |
-          NATIVE=1 ./test-libcxx-module.sh /llvm-mingw
+          ./test-libcxx-module.sh /llvm-mingw
           ./run-tests.sh /llvm-mingw
           ./run-lldb-tests.sh /llvm-mingw
 
diff --git a/test-libcxx-module.sh b/test-libcxx-module.sh
index 628a97e..3a42a5c 100755
--- a/test-libcxx-module.sh
+++ b/test-libcxx-module.sh
@@ -26,6 +26,13 @@ export PATH=$PREFIX/bin:$PATH
 
 : ${ARCHS:=${TOOLCHAIN_ARCHS-i686 x86_64 armv7 aarch64}}
 
+case $(uname) in
+MINGW*|MSYS*)
+    NATIVE=1
+    ;;
+*)
+esac
+
 for arch in $ARCHS; do
     # TODO: This should ideally use "$CXX -print-file-name=libc++.modules.json", then parse the json to find the relevant cppm file and include directory.
     $arch-w64-mingw32-clang++ -I$PREFIX/share/libc++/v1 -std=gnu++23 -Wno-reserved-module-identifier -x c++-module -fmodule-output=std.pcm -o std.cppm.obj -c $PREFIX/share/libc++/v1/std.cppm