diff --git a/.forgejo/workflows/build-iso.yml b/.forgejo/workflows/build-iso.yml
index 67c3224..195f8f9 100644
--- a/.forgejo/workflows/build-iso.yml
+++ b/.forgejo/workflows/build-iso.yml
@@ -34,7 +34,9 @@ jobs:
           sha256sum "$iso"
 
       - name: Upload ISO artifact
-        uses: actions/upload-artifact@v4
+        # v4+ isn't supported on Forgejo yet (uses newer @actions/artifact
+        # protocol that Forgejo's GHES-compatible API doesn't implement).
+        uses: actions/upload-artifact@v3
         with:
           name: furtka-iso
           path: iso/out/*.iso