diff --git a/.github/actions/install-bootstrap-dependencies/action.yml b/.github/actions/install-bootstrap-dependencies/action.yml
index c20c184b1..57c7d20b3 100644
--- a/.github/actions/install-bootstrap-dependencies/action.yml
+++ b/.github/actions/install-bootstrap-dependencies/action.yml
@@ -54,8 +54,9 @@ runs:
       shell: 'msys2 {0}'
       run: |
         # Install dependencies (windows)
-        pacboy --noconfirm -S --needed gcc:p gmp-devel:
+        pacboy --noconfirm -S --needed $(if [ ${MSYSTEM} == "CLANG64" ]; then echo clang:p ; else echo gcc:p; fi) gmp-devel:
+        if [[ "${{ inputs.install-llvm }}" == "true" ]]; then pacboy --noconfirm -S --needed llvm:p ; fi
         mkdir boot && cd boot
         curl -sOL https://github.com/MLton/mlton/releases/download/on-20241230-release/mlton-20241230-1.amd64-mingw.windows-2022_MINGW64.tgz
-        tar xzf https://github.com/MLton/mlton/releases/download/on-20241230-release/mlton-20241230-1.amd64-mingw.windows-2022_MINGW64.tgz --exclude='*/share' --strip-components=1
-        rm https://github.com/MLton/mlton/releases/download/on-20241230-release/mlton-20241230-1.amd64-mingw.windows-2022_MINGW64.tgz
+        tar xzf mlton-20241230-1.amd64-mingw.windows-2022_MINGW64.tgz --exclude='*/share' --strip-components=1
+        rm mlton-20241230-1.amd64-mingw.windows-2022_MINGW64.tgz
diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 628be3a0a..711d4e0b0 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -54,6 +54,28 @@ jobs:
             cc: "gcc"
             codegen: "c"
 
+          - runner: windows-2022
+            msystem: ucrt64
+            cc: "gcc"
+            codegen: "amd64"
+          - runner: windows-2022
+            msystem: ucrt64
+            cc: "gcc"
+            codegen: "c"
+
+          - runner: windows-2022
+            msystem: clang64
+            cc: "clang"
+            codegen: "amd64"
+          - runner: windows-2022
+            msystem: clang64
+            cc: "clang"
+            codegen: "c"
+          - runner: windows-2022
+            msystem: clang64
+            cc: "clang"
+            codegen: "llvm"
+
     runs-on: ${{ matrix.runner }}
 
     defaults:
@@ -128,11 +150,11 @@ jobs:
             $( if [[ -n "$WITH_GMP_DIR" ]]; then echo "WITH_GMP_DIR=$WITH_GMP_DIR"; fi ) \
             WITH_ALL_RUNTIME=true \
             WITH_DBG_RUNTIME=false \
-            MLTON_BINARY_RELEASE_SUFFIX=".${{ matrix.runner }}_${{ matrix.cc }}_${{ matrix.codegen }}" \
+            MLTON_BINARY_RELEASE_SUFFIX=".${{ matrix.runner }}${{ matrix.msystem && format('_msys2_{0}', matrix.msystem) || '' }}_${{ matrix.cc }}_${{ matrix.codegen }}" \
             binary-release
 
       - name: Upload Artifact
         uses: actions/upload-artifact@v4
         with:
-          name: mlton.${{ matrix.runner }}_${{ matrix.cc }}_${{ matrix.codegen }}
+          name: mlton..${{ matrix.runner }}${{ matrix.msystem && format('_msys2_{0}', matrix.msystem) || '' }}_${{ matrix.cc }}_${{ matrix.codegen }}
           path: ./*.tgz