diff -r 761b5b266985 -r b3ce838a077e hgext/evolve.py
--- a/hgext/evolve.py	Mon Feb 04 17:18:02 2013 +0100
+++ b/hgext/evolve.py	Mon Feb 04 17:21:02 2013 +0100
@@ -785,14 +785,8 @@
         nodesrc = orig.node()
         destphase = repo[nodesrc].phase()
         try:
-            if rebase.rebasenode.func_code.co_argcount == 5:
-                # rebasenode collapse argument was introduced by
-                # d1afbf03e69a (2.3)
-                r = rebase.rebasenode(repo, orig.node(), dest.node(),
-                                      {node.nullrev: node.nullrev}, False)
-            else:
-                r = rebase.rebasenode(repo, orig.node(), dest.node(),
-                                     {node.nullrev: node.nullrev})
+            r = rebase.rebasenode(repo, orig.node(), dest.node(),
+                                  {node.nullrev: node.nullrev}, False)
             if r[-1]: #some conflict
                 raise util.Abort(
                         'unresolved merge conflicts (see hg help resolve)')