--- a/mercurial/mdiff.py	Thu Nov 27 16:07:17 2008 +0100
+++ b/mercurial/mdiff.py	Thu Nov 27 17:00:54 2008 +0100
@@ -160,7 +160,7 @@
         if opts.showfunc:
             # walk backwards from the start of the context
             # to find a line starting with an alphanumeric char.
-            for x in xrange(astart, -1, -1):
+            for x in xrange(astart - 1, -1, -1):
                 t = l1[x].rstrip()
                 if funcre.match(t):
                     func = ' ' + t[:40]