   :group 'merlin)
 
 (defface merlin-type-face
-  '((t :inherit 'caml-types-expr-face))
+  '((t :inherit caml-types-expr-face))
   "Face for highlighting a typed expr."
+  :group 'merlin)
+
+(defface merlin-compilation-warning-face
+  '((t :inherit compilation-error))
+  "If non-nil, face to use to highlight merlin warnings."
+  :group 'merlin)
+
+(defface merlin-compilation-error-face
+  '((t :inherit compilation-warning))
+  "If non-nil, face to use to highlight merlin errors."
   :group 'merlin)
 
 ;;

              (if (merlin-error-warning-p (cdr (assoc 'message err)))
                  (merlin-put-margin-overlay overlay
                                             merlin-margin-warning-string
                                             merlin-compilation-warning-face)
                (merlin-put-margin-overlay overlay
                                           merlin-margin-error-string
                                           merlin-compilation-error-face))
              overlay)))
         (errors   (mapcar err-point errors)))
    (setq merlin-pending-errors errors)

(defun merlin-put-margin-overlay (overlay string &optional face)
  "Put a margin overlay inside OVERLAY, with face FACE and string STRING."
  (set-window-margins nil 1)
  (when face (overlay-put overlay 'face face))
  (overlay-put overlay 'before-string
               (propertize " " 'display `((margin left-margin) ,string))))

