diff --git a/Gemfile.lock b/Gemfile.lock
index 4f77244..f43a9af 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -1,7 +1,7 @@
 PATH
   remote: .
   specs:
-    cli-kit (5.3.0)
+    cli-kit (5.3.1)
       cli-ui (~> 2.4)
       logger (~> 1.7)
 
diff --git a/lib/cli/kit/core_ext.rb b/lib/cli/kit/core_ext.rb
index f463a36..546d2de 100644
--- a/lib/cli/kit/core_ext.rb
+++ b/lib/cli/kit/core_ext.rb
@@ -17,6 +17,7 @@ class Fault
     def to_s = raise NotImplementedError, 'abstract method called'
 
     # A bug in the tool itself (dev, tec, cli-kit, etc.).
+    # @sealed
     class System < Fault
       # @override
       #: -> String
diff --git a/lib/cli/kit/version.rb b/lib/cli/kit/version.rb
index 684f064..7e39148 100644
--- a/lib/cli/kit/version.rb
+++ b/lib/cli/kit/version.rb
@@ -2,6 +2,6 @@
 
 module CLI
   module Kit
-    VERSION = '5.3.0'
+    VERSION = '5.3.1'
   end
 end