diff --git a/docs/input-kafka.asciidoc b/docs/input-kafka.asciidoc
index a6b0e5f..afd27ae 100644
--- a/docs/input-kafka.asciidoc
+++ b/docs/input-kafka.asciidoc
@@ -286,6 +286,8 @@ This will add a field named `kafka` to the logstash event containing the followi
 * `offset`: The offset from the partition this message is associated with
 * `key`: A ByteBuffer containing the message key
 
+NOTE: Only headers whose values are valid UTF-8 byte sequences are included.
+      If an event has multiple headers with the same key, at most one will be included.
 
 [id="plugins-{type}s-{plugin}-auto_create_topics"]
 ===== `auto_create_topics`