diff --git a/.github/test-arg/lowercase.dockerfile b/.github/test-arg/lowercase.dockerfile
new file mode 100644
index 00000000..123650dc
--- /dev/null
+++ b/.github/test-arg/lowercase.dockerfile
@@ -0,0 +1,7 @@
+ARG registry='gcr.io/hdl-containers/debian/bullseye'
+
+FROM $registry/build/build AS build
+
+ARG registry
+
+COPY --from=$registry/pkg/icestorm /icestorm/usr/local/share/icebox /usr/local/share/icebox
diff --git a/.github/test-arg/mount-lowercase.dockerfile b/.github/test-arg/mount-lowercase.dockerfile
new file mode 100644
index 00000000..20bbd218
--- /dev/null
+++ b/.github/test-arg/mount-lowercase.dockerfile
@@ -0,0 +1,10 @@
+# syntax=docker/dockerfile:1.2
+
+ARG registry='docker.io/hdlc'
+
+FROM $registry/build:build AS build
+
+ARG registry
+
+RUN --mount=type=cache,from=$registry/pkg:icestorm,src=/icestorm/usr/local/share/icebox,target=/usr/local/share/icebox \
+  ls -la /usr/local/share/icebox
diff --git a/.github/test-arg/mount-uppercase.dockerfile b/.github/test-arg/mount-uppercase.dockerfile
new file mode 100644
index 00000000..a14b9ae9
--- /dev/null
+++ b/.github/test-arg/mount-uppercase.dockerfile
@@ -0,0 +1,10 @@
+# syntax=docker/dockerfile:1.2
+
+ARG REGISTRY='docker.io/hdlc'
+
+FROM $REGISTRY/build:build AS build
+
+ARG REGISTRY
+
+RUN --mount=type=cache,from=$REGISTRY/pkg:icestorm,src=/icestorm/usr/local/share/icebox,target=/usr/local/share/icebox \
+  ls -la /usr/local/share/icebox
diff --git a/.github/test-arg/uppercase.dockerfile b/.github/test-arg/uppercase.dockerfile
new file mode 100644
index 00000000..43769588
--- /dev/null
+++ b/.github/test-arg/uppercase.dockerfile
@@ -0,0 +1,7 @@
+ARG REGISTRY='gcr.io/hdl-containers/debian/bullseye'
+
+FROM $REGISTRY/build/build AS build
+
+ARG REGISTRY
+
+COPY --from=$REGISTRY/pkg/icestorm /icestorm/usr/local/share/icebox /usr/local/share/icebox
diff --git a/.github/test-arg/workaround.dockerfile b/.github/test-arg/workaround.dockerfile
new file mode 100644
index 00000000..c61f74a2
--- /dev/null
+++ b/.github/test-arg/workaround.dockerfile
@@ -0,0 +1,8 @@
+ARG REGISTRY='gcr.io/hdl-containers/debian/bullseye'
+
+# WORKAROUND: this is required because 'COPY --from' does not support ARGs
+FROM $REGISTRY/pkg/icestorm AS pkg-icestorm
+
+FROM $REGISTRY/build/build AS build
+
+COPY --from=pkg-icestorm /icestorm/usr/local/share/icebox /usr/local/share/icebox
diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
new file mode 100644
index 00000000..bdf49591
--- /dev/null
+++ b/.github/workflows/test.yml
@@ -0,0 +1,29 @@
+name: 'test-arg'
+
+on:
+  push:
+
+env:
+  DOCKER_BUILDKIT: 1
+
+jobs:
+
+  test:
+    runs-on: ubuntu-latest
+    strategy:
+      fail-fast: false
+      matrix:
+        dfile:
+          - workaround
+          - uppercase
+          - lowercase
+          - mount-uppercase
+          - mount-lowercase
+
+    env:
+      HDL_ARCH: ${{ matrix.arch }}
+    steps:
+
+    - uses: actions/checkout@v2
+
+    - run: docker build -t test/img - < .github/test-arg/${{ matrix.dfile }}.dockerfile