diff --git a/hgext/rebase.py b/hgext/rebase.py
--- a/hgext/rebase.py
+++ b/hgext/rebase.py
@@ -658,6 +658,7 @@ def clearstatus(repo):
 def restorestatus(repo):
     'Restore a previously stored status'
     try:
+        keepbranches = None
         target = None
         collapse = False
         external = nullrev
@@ -687,6 +688,10 @@ def restorestatus(repo):
                     state[repo[oldrev].rev()] = int(newrev)
                 else:
                     state[repo[oldrev].rev()] = repo[newrev].rev()
+
+        if keepbranches is None:
+            raise util.Abort(_('.hg/rebasestate is incomplete'))
+
         skipped = set()
         # recompute the set of skipped revs
         if not collapse:
diff --git a/tests/test-rebase-abort.t b/tests/test-rebase-abort.t
--- a/tests/test-rebase-abort.t
+++ b/tests/test-rebase-abort.t
@@ -13,6 +13,16 @@
   $ hg init a
   $ cd a
 
+  $ touch .hg/rebasestate
+  $ hg sum
+  parent: -1:000000000000 tip (empty repository)
+  branch: default
+  commit: (clean)
+  update: (current)
+  abort: .hg/rebasestate is incomplete
+  [255]
+  $ rm .hg/rebasestate
+
   $ echo c1 > common
   $ hg add common
   $ hg ci -m C1