diff --git a/.gitea/workflows/build.yml b/.gitea/workflows/build.yml
index a65de39..78bad45 100644
--- a/.gitea/workflows/build.yml
+++ b/.gitea/workflows/build.yml
@@ -76,8 +76,12 @@ jobs:
           # Attach zips and the signed xpi (if present) as release assets
           for f in dist/*.zip dist/*.xpi; do
             [ -f "$f" ] || continue
+            NAME="$(basename "$f")"
+            # URL-encode the asset name so '+' (in 'ismis-helper-1.4.0-an+fx.xpi')
+            # survives the query string instead of being decoded to a space.
+            ENC=$(python3 -c "import urllib.parse,sys; print(urllib.parse.quote(sys.argv[1], safe=''))" "$NAME")
             curl -sS -X POST \
               -H "Authorization: token ${GITHUB_TOKEN}" \
               -F "attachment=@${f}" \
-              "${API}/repos/${REPO}/releases/${RELEASE_ID}/assets?name=$(basename "${f}")"
+              "${API}/repos/${REPO}/releases/${RELEASE_ID}/assets?name=${ENC}"
           done
\ No newline at end of file