diff --git a/docker-build-nix/action.yaml b/docker-build-nix/action.yaml
index b79ce38..1680db6 100644
--- a/docker-build-nix/action.yaml
+++ b/docker-build-nix/action.yaml
@@ -91,6 +91,9 @@ runs:
         export TMPDIR="${TMPDIR:-/tmp}"
         mkdir -p "$TMPDIR"
 
+        # Ensure /var/tmp exists as fallback (skopeo may use this)
+        sudo mkdir -p /var/tmp 2>/dev/null || mkdir -p /var/tmp || true
+
         # Build skopeo command with optional credentials
         SKOPEO_CMD="skopeo copy"
         if [ -n "${{ inputs.registry-username }}" ] && [ -n "${{ inputs.registry-password }}" ]; then