diff --git a/mercurial/localrepo.py b/mercurial/localrepo.py
--- a/mercurial/localrepo.py
+++ b/mercurial/localrepo.py
@@ -1354,6 +1354,22 @@ class localrepository(repo.repository):
                     added.append(fn)
             removed = mf1.keys()
 
+        if working and modified and not self.dirstate._checklink:
+            # Symlink placeholders may get non-symlink-like contents
+            # via user error or dereferencing by NFS or Samba servers,
+            # so we filter out any placeholders that don't look like a
+            # symlink
+            sane = []
+            for f in modified:
+                if ctx2.flags(f) == 'l':
+                    d = ctx2[f].data()
+                    if len(d) >= 1024 or '\n' in d or util.binary(d):
+                        self.ui.debug('ignoring suspect symlink placeholder'
+                                      ' "%s"\n' % f)
+                        continue
+                sane.append(f)
+            modified = sane
+
         r = modified, added, removed, deleted, unknown, ignored, clean
 
         if listsubrepos:
diff --git a/tests/test-symlink-placeholder.t b/tests/test-symlink-placeholder.t
new file mode 100644
--- /dev/null
+++ b/tests/test-symlink-placeholder.t
@@ -0,0 +1,68 @@
+Create extension that can disable symlink support:
+
+  $ cat > nolink.py <<EOF
+  > from mercurial import extensions, util
+  > def setflags(orig, f, l, x):
+  >     pass
+  > def checklink(orig, path):
+  >     return False
+  > def extsetup(ui):
+  >     extensions.wrapfunction(util, 'setflags', setflags)
+  >     extensions.wrapfunction(util, 'checklink', checklink)
+  > EOF
+
+  $ hg init unix-repo
+  $ cd unix-repo
+  $ echo foo > a
+  $ ln -s a b
+  $ hg ci -Am0
+  adding a
+  adding b
+  $ cd ..
+
+Simulate a checkout shared on NFS/Samba:
+
+  $ hg clone -q unix-repo shared
+  $ cd shared
+  $ rm b
+  $ echo foo > b
+  $ hg --config extensions.n=$TESTTMP/nolink.py status --debug
+  ignoring suspect symlink placeholder "b"
+
+Make a clone using placeholders:
+
+  $ hg --config extensions.n=$TESTTMP/nolink.py clone . ../win-repo
+  updating to branch default
+  2 files updated, 0 files merged, 0 files removed, 0 files unresolved
+  $ cd ../win-repo
+  $ cat b
+  a (no-eol)
+  $ hg --config extensions.n=$TESTTMP/nolink.py st --debug
+
+Write binary data to the placeholder:
+
+  >>> open('b', 'w').write('this is a binary\0')
+  $ hg --config extensions.n=$TESTTMP/nolink.py st --debug
+  ignoring suspect symlink placeholder "b"
+
+Write a long string to the placeholder:
+
+  >>> open('b', 'w').write('this' * 1000)
+  $ hg --config extensions.n=$TESTTMP/nolink.py st --debug
+  ignoring suspect symlink placeholder "b"
+
+Commit shouldn't succeed:
+
+  $ hg --config extensions.n=$TESTTMP/nolink.py ci -m1
+  nothing changed
+  [1]
+
+Write a valid string to the placeholder:
+
+  >>> open('b', 'w').write('this')
+  $ hg --config extensions.n=$TESTTMP/nolink.py st --debug
+  M b
+  $ hg --config extensions.n=$TESTTMP/nolink.py ci -m1
+  $ hg manifest tip --verbose
+  644   a
+  644 @ b