Index: Misc/python-mode.el
===================================================================
--- Misc/python-mode.el	(revision 56963)
+++ Misc/python-mode.el	(working copy)
@@ -400,6 +400,8 @@
      ;; block introducing keywords with immediately following colons.
      ;; Yes "except" is in both lists.
      (cons (concat "\\b\\(" kw2 "\\)[ \n\t(]") 1)
+     ;; lambda form without arguments.
+     (cons (concat "\\b\\(lambda\\):[ \n\t(]") 1)
      ;; `as' but only in "import foo as bar"
      '("[ \t]*\\(\\bfrom\\b.*\\)?\\bimport\\b.*\\b\\(as\\)\\b" . 2)
      ;; classes