diff --git a/ubuntu/mastodon.zombocloud.com.yml b/ubuntu/mastodon.zombocloud.com.yml
index be1bd5a..2baebe9 100644
--- a/ubuntu/mastodon.zombocloud.com.yml
+++ b/ubuntu/mastodon.zombocloud.com.yml
@@ -31,7 +31,7 @@
             try_files $uri @proxy;
           }
         - location ~ ^/(emoji|packs|system/media_attachments/files|system/accounts/avatars) {
-            add_header Cache-Control public, max-age=31536000, immutable;
+            add_header Cache-Control "public, max-age=31536000, immutable";
           }
         - location @proxy {
             proxy_set_header Host $host;