diff --git a/.github/workflows/build.yml b/.github/workflows/build.yml
index 1fcf523..0d2f144 100644
--- a/.github/workflows/build.yml
+++ b/.github/workflows/build.yml
@@ -133,6 +133,14 @@ jobs:
           username: ${{ github.actor }}
           password: ${{ secrets.GITHUB_TOKEN }}
 
+      # Workaround bug where capital letters in your GitHub username make it impossible to push to GHCR.
+      # https://github.com/macbre/push-to-ghcr/issues/12
+      - name: Lowercase Registry
+        id: registry_case
+        uses: ASzc/change-string-case-action@v6
+        with:
+          string: ${{ env.IMAGE_REGISTRY }}
+
       - name: Push To GHCR
         uses: redhat-actions/push-to-registry@5ed88d269cf581ea9ef6dd6806d01562096bee9c # v2
         if: github.event_name != 'pull_request' && github.ref == format('refs/heads/{0}', github.event.repository.default_branch)
@@ -141,7 +149,7 @@ jobs:
           REGISTRY_USER: ${{ github.actor }}
           REGISTRY_PASSWORD: ${{ github.token }}
         with:
-          registry: ${{ env.IMAGE_REGISTRY }}
+          registry: ${{ steps.registry_case.outputs.lowercase }}
           image: ${{ env.IMAGE_NAME }}
           tags: ${{ steps.metadata.outputs.tags }}
           username: ${{ env.REGISTRY_USER }}