diff --git a/doc/notes/notes-current.rst b/doc/notes/notes-current.rst
index 23dae45db3..35cf3cdf0e 100644
--- a/doc/notes/notes-current.rst
+++ b/doc/notes/notes-current.rst
@@ -19,7 +19,11 @@ Security Fixes
 Known Issues
 ~~~~~~~~~~~~
 
-- None.
+- The ``named`` daemon uses load-balanced sockets to increase performance by
+  distributing the incoming queries among multiple threads.  Currently, the only
+  operating systems that support load-balanced sockets are Linux and FreeBSD 12,
+  thus both UDP and TCP performance is limited to a single-thread on systems
+  without load-balancing socket support. [GL #2137]
 
 New Features
 ~~~~~~~~~~~~