diff --git a/source/reference/expansion-directives.txt b/source/reference/expansion-directives.txt
index 4efa7163655..6d998bb4727 100644
--- a/source/reference/expansion-directives.txt
+++ b/source/reference/expansion-directives.txt
@@ -194,7 +194,7 @@ entire configuration file.
               path: "/var/log/mongodb/mongod.log"
             net:
               bindIp: 192.51.100.24,127.0.0.1
-              TLS:
+              tls:
                 mode: requireTLS
                 certificateKeyFile: "/etc/tls/mongod.pem"
                 certificateKeyFilePassword: