diff --git a/compat-30.el b/compat-30.el
index e0a8def..6c5db9e 100644
--- a/compat-30.el
+++ b/compat-30.el
@@ -285,7 +285,7 @@ Other types are considered unordered and the return value will be ‘nil’."
    ;; Other values of equal type are considered unordered (return value nil).
    ((eq (type-of a) (type-of b)) nil)
    ;; Different types.
-   (t (error "value< unsupported type: %S %S" a b))))
+   (t (error "value< type mismatch: %S %S" a b))))
 
 (compat-defun sort (seq &optional lessp &rest rest) ;; <compat-tests:sort>
   "Sort function with support for keyword arguments.