diff --git a/hgext/largefiles/reposetup.py b/hgext/largefiles/reposetup.py
--- a/hgext/largefiles/reposetup.py
+++ b/hgext/largefiles/reposetup.py
@@ -156,7 +156,11 @@ def reposetup(ui, repo):
                                 ignored, clean) = s
                         if parentworking:
                             for lfile in unsure:
-                                if ctx1[lfutil.standin(lfile)].data().strip() \
+                                standin = lfutil.standin(lfile)
+                                if standin not in ctx1:
+                                    # from second parent
+                                    modified.append(lfile)
+                                elif ctx1[standin].data().strip() \
                                         != lfutil.hashfile(self.wjoin(lfile)):
                                     modified.append(lfile)
                                 else:
diff --git a/tests/test-largefiles.t b/tests/test-largefiles.t
--- a/tests/test-largefiles.t
+++ b/tests/test-largefiles.t
@@ -645,6 +645,23 @@ been very problematic).
   $ cat sub2/large7
   large7
 
+Test status after merging with a branch that introduces a new largefile:
+
+  $ echo large > large
+  $ hg add --large large
+  $ hg commit -m 'add largefile'
+  $ hg update -q ".^"
+  $ echo change >> normal3
+  $ hg commit -m 'some change'
+  created new head
+  $ hg merge
+  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
+  (branch merge, don't forget to commit)
+  getting changed largefiles
+  1 largefiles updated, 0 removed
+  $ hg status
+  M large
+
 Test that a normal file and a largefile with the same name and path cannot
 coexist.