diff --git a/actions/setup-conftest/action.yaml b/actions/setup-conftest/action.yaml
index 2d4163599..081bed38b 100644
--- a/actions/setup-conftest/action.yaml
+++ b/actions/setup-conftest/action.yaml
@@ -18,6 +18,10 @@ runs:
         path: ${{ github.workspace }}/bin/conftest
         key: conftest-${{ runner.os }}-${{ runner.arch }}-${{ inputs.version }}
 
+    - if: runner.os == 'macOS'
+      shell: sh
+      run: echo "OS=Darwin" >> "$GITHUB_ENV"
+
     # runner.arch options: X86, X64, ARM, or ARM64.
     # conftest release: arm64, x86_64, ppc64le, s390x.
     # If it ain't arm64 or x86_64, it'll fall back to runner.arch.
@@ -36,7 +40,7 @@ runs:
       with:
         repo: "open-policy-agent/conftest"
         version: "tags/v${{ inputs.version }}"
-        file: "conftest_${{ inputs.version }}_${{ runner.os }}_${{ env.ARCH || runner.arch }}.tar.gz"
+        file: "conftest_${{ inputs.version }}_${{ env.OS || runner.os }}_${{ env.ARCH || runner.arch }}.tar.gz"
         target: ${{ github.workspace }}/bin/conftest.tgz
 
     - name: Unpack tarball