diff --git a/.forgejo/workflows/deploy.yml b/.forgejo/workflows/deploy.yml
index dc8bf8b..bff47fa 100644
--- a/.forgejo/workflows/deploy.yml
+++ b/.forgejo/workflows/deploy.yml
@@ -41,6 +41,12 @@ jobs:
 
       - name: Log in to the Forgejo registry
         run: |
+          # Isolate Docker's config in a throwaway dir (outside the build context)
+          # so login doesn't use the desktop's credential helper (credsStore: pass,
+          # uninitialised on the runner). Exported so build/push see it too.
+          export DOCKER_CONFIG="${RUNNER_TEMP}/docker"
+          echo "DOCKER_CONFIG=${DOCKER_CONFIG}" >> "$GITHUB_ENV"
+          mkdir -p "${DOCKER_CONFIG}"
           echo "${{ secrets.REGISTRY_TOKEN }}" \
             | docker login "${REGISTRY}" -u "${{ secrets.REGISTRY_USER }}" --password-stdin