diff --git a/lib/internal/streams/destroy.js b/lib/internal/streams/destroy.js
index 8708ca022c7f8d..ded75b255934c4 100644
--- a/lib/internal/streams/destroy.js
+++ b/lib/internal/streams/destroy.js
@@ -22,7 +22,8 @@ function needError(stream, err) {
   return true;
 }
 
-// Undocumented cb() API, needed for core, not for public API
+// Undocumented cb() API, needed for core, not for public API.
+// The cb() will be invoked synchronously if _destroy is synchronous.
 function destroy(err, cb) {
   const r = this._readableState;
   const w = this._writableState;