diff --git a/portainer.subfolder.conf.sample b/portainer.subfolder.conf.sample
index fafed86..6157ead 100644
--- a/portainer.subfolder.conf.sample
+++ b/portainer.subfolder.conf.sample
@@ -36,5 +36,7 @@ location ^~ /portainer/api/websocket/ {
     proxy_pass $upstream_proto://$upstream_app:$upstream_port;
 
     rewrite /portainer(.*) $1 break;
+    proxy_set_header Upgrade $http_upgrade;
+    proxy_set_header Connection "upgrade";
     proxy_hide_header X-Frame-Options; # Possibly not needed after Portainer 1.20.0
 }