diff --git a/backend/templates/_listen.conf b/backend/templates/_listen.conf
index 50b1f1f3b..775d9e2b8 100644
--- a/backend/templates/_listen.conf
+++ b/backend/templates/_listen.conf
@@ -10,7 +10,7 @@
   listen 443 quic;
   listen [::]:443 quic;
 
-  more_set_headers "Alt-Svc: h3=':443'; ma=86400";
+  more_set_headers 'Alt-Svc: h3=":443"; ma=86400';
 {% endif %}
 {% endif %}
 {% unless hsts_subdomains %}