diff --git a/lisp/simple.el b/lisp/simple.el
index bb28145502..2acceef6a1 100644
--- a/lisp/simple.el
+++ b/lisp/simple.el
@@ -1964,13 +1964,14 @@ read-extended-command
      #'commandp t nil 'extended-command-history)))
 
 (defun read-extended-command--annotation (command-name)
-  (let* ((fun (and (stringp command-name) (intern-soft command-name)))
+  "Return annotation for COMMAND-NAME in M-x completion."
+  (let* ((fun (intern-soft command-name))
          (binding (where-is-internal fun overriding-local-map t))
          (obsolete (get fun 'byte-obsolete-info))
          (alias (symbol-function fun)))
     (cond ((symbolp alias)
            (format " (%s)" alias))
-          (obsolete
+          ((car obsolete)
            (format " (%s)" (car obsolete)))
           ((and binding (not (stringp binding)))
            (format " (%s)" (key-description binding))))))