diff --git a/devel/yaml_api.md b/devel/yaml_api.md
index 6113f0f..0e7781f 100644
--- a/devel/yaml_api.md
+++ b/devel/yaml_api.md
@@ -1983,6 +1983,9 @@ Each route entry could have these parameters:
    route as `state: absnet` and append new route.
  * `vrf-name`: String. Store the route to the route table which specified VRF
    is binding to.
+ * `lock-mtu`: Boolean. New in version 2.2.59. When set to true, the route MTU
+   is locked, preventing Path MTU Discovery (PMTUD) from automatically
+   adjusting it.
 
 ## Route Rules