diff --git a/docs/plugins/reindex.asciidoc b/docs/plugins/reindex.asciidoc
index 87e6796e860..c4bdb60f8b8 100644
--- a/docs/plugins/reindex.asciidoc
+++ b/docs/plugins/reindex.asciidoc
@@ -460,12 +460,19 @@ POST /_reindex
 === URL Parameters
 
 In addition to the standard parameters like `pretty`, all APIs in this plugin
-support `refresh`, `consistency`, and `timeout`.
+support `refresh`, `wait_for_completion`, `consistency`, and `timeout`.
 
 Sending the `refresh` url parameter will cause all indexes to which the request
 wrote to be refreshed. This is different than the Index API's `refresh`
 parameter which causes just the shard that received the new data to be indexed.
 
+If the request contains `wait_for_completion=false` then Elaasticsearch will
+perform some preflight checks, launch the request, and then return a `task`
+which can be used with {ref}/tasks.html[Tasks APIs] to cancel or get the status
+of the task. For now, once the request is finished the task is gone and the
+only place to look for the ultimate result of the task is in the Elasticsearch
+log file. This be fixed soon.
+
 `consistency` controls how many copies of a shard must respond to each write
 request. `timeout` controls how long each write request waits for unavailable
 shards to become available. Both work exactly how they work in the