diff -r 7000825ef3ba -r c5db9581bfa6 mercurial/commands.py
--- a/mercurial/commands.py	Fri Jul 22 08:47:35 2005 +0100
+++ b/mercurial/commands.py	Fri Jul 22 08:58:16 2005 +0100
@@ -615,7 +615,8 @@
         parenttags = ['/'.join(tags)
                       for tags in map(repo.nodetags, parents) if tags]
         # tags for multiple parents separated by ' + '
-        output.append(' + '.join(parenttags))
+        if parenttags:
+            output.append(' + '.join(parenttags))
 
     ui.write("%s\n" % ' '.join(output))