--- a/hgext/evolve.py	Mon Feb 04 17:55:03 2013 +0100
+++ b/hgext/evolve.py	Mon Feb 04 18:07:09 2013 +0100
@@ -1259,19 +1259,24 @@
     wlock = repo.wlock()
     try:
         lock = repo.lock()
-        new = set(scmutil.revrange(repo, succs))
-        targetnodes = set(scmutil.revrange(repo, revs))
-        if not targetnodes:
+        precs = []
+        for p in sorted(set(scmutil.revrange(repo, revs))):
+            cp = repo[p]
+            precs.append(cp)
+        if not precs:
             raise util.Abort('nothing to prune')
-        if new:
-            sucs = tuple(repo[n] for n in new)
         else:
             sucs = ()
+
+        sucs = tuple(repo[n]
+                     for n in sorted(set(scmutil.revrange(repo, succs))))
+        if len(sucs) > 1 and len(precs) > 1:
+            msg = "Can't use multiple successors for multiple precursors"
+            raise util.Abort(msg)
         markers = []
-        for n in targetnodes:
-            markers.append((repo[n], sucs))
+        for p in precs:
+            markers.append((p, sucs))
         createmarkers(repo, markers)
-
         # update to an unkilled parent
         wdp = repo['.']
         newnode = wdp