diff --git a/group_vars/matrix_servers b/group_vars/matrix_servers
index 394e26dc9..8d3922764 100755
--- a/group_vars/matrix_servers
+++ b/group_vars/matrix_servers
@@ -1578,7 +1578,7 @@ matrix_nginx_proxy_proxy_synapse_enabled: "{{ matrix_synapse_enabled }}"
 matrix_nginx_proxy_proxy_synapse_client_api_addr_with_container: "matrix-synapse:{{ matrix_synapse_container_client_api_port }}"
 matrix_nginx_proxy_proxy_synapse_client_api_addr_sans_container: "127.0.0.1:{{ matrix_synapse_container_client_api_port }}"
 matrix_nginx_proxy_proxy_synapse_federation_api_addr_with_container: "matrix-synapse:{{matrix_synapse_container_federation_api_plain_port|string}}"
-matrix_nginx_proxy_proxy_synapse_federation_api_addr_sans_container: "localhost:{{matrix_synapse_container_federation_api_plain_port|string}}"
+matrix_nginx_proxy_proxy_synapse_federation_api_addr_sans_container: "127.0.0.1:{{matrix_synapse_container_federation_api_plain_port|string}}"
 
 matrix_nginx_proxy_proxy_dendrite_enabled: "{{ matrix_dendrite_enabled }}"
 matrix_nginx_proxy_proxy_dendrite_client_api_addr_with_container: "matrix-dendrite:{{ matrix_dendrite_http_bind_port|string }}"
diff --git a/roles/matrix-nginx-proxy/defaults/main.yml b/roles/matrix-nginx-proxy/defaults/main.yml
index f19eb4ab0..195b16fd9 100644
--- a/roles/matrix-nginx-proxy/defaults/main.yml
+++ b/roles/matrix-nginx-proxy/defaults/main.yml
@@ -311,7 +311,7 @@ matrix_nginx_proxy_proxy_matrix_client_redirect_root_uri_to_domain: ""
 # Controls whether proxying for the Matrix Federation API should be done.
 matrix_nginx_proxy_proxy_matrix_federation_api_enabled: false
 matrix_nginx_proxy_proxy_matrix_federation_api_addr_with_container: "matrix-nginx-proxy:12088"
-matrix_nginx_proxy_proxy_matrix_federation_api_addr_sans_container: "localhost:12088"
+matrix_nginx_proxy_proxy_matrix_federation_api_addr_sans_container: "127.0.0.1:12088"
 matrix_nginx_proxy_proxy_matrix_federation_api_client_max_body_size_mb: "{{ (matrix_nginx_proxy_proxy_matrix_client_api_client_max_body_size_mb | int) * 3 }}"
 matrix_nginx_proxy_proxy_matrix_federation_api_ssl_certificate: "{{ matrix_ssl_config_dir_path }}/live/{{ matrix_nginx_proxy_proxy_matrix_hostname }}/fullchain.pem"
 matrix_nginx_proxy_proxy_matrix_federation_api_ssl_certificate_key: "{{ matrix_ssl_config_dir_path }}/live/{{ matrix_nginx_proxy_proxy_matrix_hostname }}/privkey.pem"