diff --git a/index.md b/index.md
index ee65b00..f68503b 100644
--- a/index.md
+++ b/index.md
@@ -49,6 +49,7 @@ Setup a [matrix-synapse](https://github.com/matrix-org/synapse) chat server. Mat
   * [matrix_rc_login_address](#matrix_rc_login_address)
   * [matrix_restart_policy](#matrix_restart_policy)
   * [matrix_server_url](#matrix_server_url)
+  * [matrix_signing_key](#matrix_signing_key)
   * [matrix_tls_cert_path](#matrix_tls_cert_path)
   * [matrix_tls_cert_source](#matrix_tls_cert_source)
   * [matrix_tls_dhparam_path](#matrix_tls_dhparam_path)
@@ -422,6 +423,14 @@ matrix_restart_policy: on-failure
 matrix_server_url: example.com
 ```
 
+### matrix_signing_key
+
+#### Default value
+
+```YAML
+matrix_signing_key: _unset_
+```
+
 ### matrix_tls_cert_path
 
 #### Default value