diff -r a259f7b488ab -r 3bff26f67169 hgext/rebase.py
--- a/hgext/rebase.py	Sat Nov 16 15:46:29 2013 -0500
+++ b/hgext/rebase.py	Sun Nov 17 18:21:58 2013 -0500
@@ -226,7 +226,11 @@
                                        'nothing to rebase'))
             elif srcf:
                 src = scmutil.revrange(repo, [srcf])
+                if not src:
+                    raise util.Abort(_('empty "source" revision set - '
+                                       'nothing to rebase'))
                 rebaseset = repo.revs('(%ld)::', src)
+                assert rebaseset
             else:
                 base = scmutil.revrange(repo, [basef or '.'])
                 rebaseset = repo.revs(