diff --git a/puppet/zulip/files/nginx/zulip-include-app.d/external-sso.conf b/puppet/zulip/files/nginx/zulip-include-app.d/external-sso.conf
index 400029a711..2b0cc6eb63 100644
--- a/puppet/zulip/files/nginx/zulip-include-app.d/external-sso.conf
+++ b/puppet/zulip/files/nginx/zulip-include-app.d/external-sso.conf
@@ -4,5 +4,6 @@
 # identified the user.
 location /accounts/login/sso/ {
     proxy_pass https://localhost:8888;
+    proxy_set_header Host $host;
     proxy_next_upstream off;
 }