diff --git a/lib/rules/subsystem.js b/lib/rules/subsystem.js
index 06773a7..963df24 100644
--- a/lib/rules/subsystem.js
+++ b/lib/rules/subsystem.js
@@ -40,7 +40,6 @@ const validSubsystems = [
   'constants',
   'crypto',
   'debugger',
-  'diagnostics_channel',
   'dgram',
   'diagnostics_channel',
   'dns',