--- a/mercurial/merge.py	Mon Jun 08 18:14:44 2009 -0500
+++ b/mercurial/merge.py	Mon Jun 08 18:14:44 2009 -0500
@@ -131,11 +131,14 @@
 
     m1 = p1.manifest()
     m2 = p2.manifest()
-    ma = pa.manifest()
     backwards = (pa == p2)
 
-    if backwards or overwrite:
+    if overwrite:
         ma = m1
+    elif backwards:
+        ma = p1.p1().manifest()
+    else:
+        ma = pa.manifest()
 
     action = []
     copy, copied, diverge = {}, {}, {}