diff --git a/docs/static/running-logstash-command-line.asciidoc b/docs/static/running-logstash-command-line.asciidoc
index cb74e6d3a..93a4b107c 100644
--- a/docs/static/running-logstash-command-line.asciidoc
+++ b/docs/static/running-logstash-command-line.asciidoc
@@ -157,6 +157,15 @@ With this command, Logstash concatenates three config files, `/tmp/one`, `/tmp/t
   When creating pipeline batches, how long to wait while polling for the next event. This option defines
   how long in milliseconds to wait while polling for the next event before dispatching an undersized batch
   to filters and outputs. The default is 50ms.
+  
+  *`--pipeline.ecs_compatibility MODE`*::
+  Sets the process default value for  ECS compatibility mode.
+  Can be an ECS version like `v1` or `v8`, or `disabled`.
+  The default is `disabled`.
+  In Logstash 8, ECS compatibility will be enabled by default.
+  To prepare for an upgrade to Logstash 8, you can lock-in the Logstash 7 behavior for an individual pipeline by setting `pipeline.ecs_compatibility: disabled` in its `pipelines.yml` definition. Doing so will ensure that a migrated pipeline will continue to operate as it does in Logstash 7.
+  Using the command-line flag will set the default for _all_ pipelines, including new ones.
+  See <<ecs-compatibility>> for more info.
 
 *`--pipeline.unsafe_shutdown`*::
   Force Logstash to exit during shutdown even if there are still inflight events