diff --git a/lisp/progmodes/python.el b/lisp/progmodes/python.el
index 974e07c3c6a..fd196df7550 100644
--- a/lisp/progmodes/python.el
+++ b/lisp/progmodes/python.el
@@ -6094,7 +6094,8 @@ Optional argument REGEXP selects variables to clone and defaults
 to \"^python-\"."
   (mapc
    (lambda (pair)
-     (and (symbolp (car pair))
+     (and (consp pair)
+          (symbolp (car pair))
           (string-match (or regexp "^python-")
                         (symbol-name (car pair)))
           (set (make-local-variable (car pair))