diff --git a/Dockerfile b/Dockerfile
index 14bff92..79fc7dc 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -1,3 +1,9 @@
 FROM caddy:2
 COPY Caddyfile /etc/caddy/Caddyfile
 COPY dist/ /srv/fieldwork/
+
+# A CDN in front of the site may cache /style.css for hours. Version its URL by content hash
+# so a changed stylesheet is always fetched fresh. The build fails if the rewrite did not apply.
+RUN h=$(md5sum /srv/fieldwork/style.css | cut -c1-10) \
+ && sed -i "s|href=\"style.css\"|href=\"style.css?v=${h}\"|" /srv/fieldwork/index.html \
+ && grep -q "style.css?v=${h}" /srv/fieldwork/index.html