diff --git a/which-key.el b/which-key.el
index 600f02f..dce9718 100644
--- a/which-key.el
+++ b/which-key.el
@@ -106,7 +106,7 @@ before.  Truncation is done using `which-key-ellipsis'."
 (defcustom which-key-min-column-description-width 0
   "Every column should at least have this width."
   :group 'which-key
-  :type 'integer
+  :type 'natnum
   :version "1.0")
 
 (defcustom which-key-add-column-padding 0