diff --git a/cl-tui.asd b/cl-tui.asd
index 86b7784..38b5a9a 100644
--- a/cl-tui.asd
+++ b/cl-tui.asd
@@ -2,7 +2,7 @@
 (asdf:defsystem :cl-tui
   :description "Reusable Common Lisp Terminal UI Framework"
   :author "Amr Gharbeia"
-  :version "0.3.0"
+  :version "0.4.0"
   :license "TBD"
   :depends-on (:fiveam)
   :components
diff --git a/src/components/theme-tests.lisp b/src/components/theme-tests.lisp
index b342719..da0f669 100644
--- a/src/components/theme-tests.lisp
+++ b/src/components/theme-tests.lisp
@@ -48,7 +48,7 @@
 (test load-preset-unknown-warns
   "Unknown preset warns but doesn't error"
   (let ((th (make-theme)))
-    (load-preset th :nonexistent)
+    (signals warning (load-preset th :nonexistent))
     (is (null (theme-color th :primary)))))
 
 (test preset-switch-mode
diff --git a/src/components/theme.lisp b/src/components/theme.lisp
index a2c3f45..487933a 100644
--- a/src/components/theme.lisp
+++ b/src/components/theme.lisp
@@ -22,6 +22,7 @@
 (defmacro define-preset (name &key dark light)
   "Define a theme preset with DARK and LIGHT variants.
 NAME should be a keyword (e.g., :default, :nord)."
+  (check-type name keyword)
   `(setf (gethash ,name *presets*) '(:dark ,dark :light ,light)))
 
 (defun load-preset (theme preset-name)