diff --git a/doc/api/diagnostics_channel.md b/doc/api/diagnostics_channel.md
index 1167a591f353b2..a8217a87ca226e 100644
--- a/doc/api/diagnostics_channel.md
+++ b/doc/api/diagnostics_channel.md
@@ -267,10 +267,13 @@ added:
 changes:
   - version: REPLACEME
     pr-url: https://github.com/nodejs/node/pull/40433
-    description: Added to channels without subscribers.
+    description:
+      - Added return value.
+      - Added to channels without subscribers.
 -->
 
 * `onMessage` {Function} The previous subscribed handler to remove
+* Returns: {boolean} `true` if the handler was found, `false` otherwise.
 
 Remove a message handler previously registered to this channel with
 [`channel.subscribe(onMessage)`][].