diff --git a/remotefilelog/shallowbundle.py b/remotefilelog/shallowbundle.py
--- a/remotefilelog/shallowbundle.py
+++ b/remotefilelog/shallowbundle.py
@@ -44,6 +44,17 @@
 
     yield self.close()
 
+def _cansendflat(repo, mfnodes):
+    if not util.safehasattr(repo.manifestlog, '_revlog'):
+        return False
+
+    revlog = repo.manifestlog._revlog
+    for mfnode in mfnodes:
+        if mfnode not in revlog.nodemap:
+            return False
+
+    return True
+
 @shallowutil.interposeclass(changegroup, 'cg1packer')
 class shallowcg1packer(changegroup.cg1packer):
     def generate(self, commonrevs, clnodes, fastpathlinkrev, source):
@@ -73,9 +84,7 @@
                 core generatemanifests method, whose length depends on the
                 version of core Hg.
         """
-        sendflat = self._repo.ui.configbool('treemanifest', 'sendflat',
-                                            True)
-        if sendflat:
+        if _cansendflat(self._repo, mfs.keys()):
             # In this code path, generating the manifests populates fnodes for
             # us.
             chunks = super(shallowcg1packer, self).generatemanifests(
@@ -241,12 +250,10 @@
             for chunk in chunks:
                 yield chunk
 
-            sendflat = self._repo.ui.configbool('treemanifest', 'sendflat',
-                                                True)
             # If we're not sending flat manifests, then the subclass
             # generatemanifests call did not add the appropriate closing chunk
             # for a changegroup3.
-            if not sendflat:
+            if not _cansendflat(self._repo, mfs.keys()):
                 yield self._manifestsdone()
 
 # Unused except in older versions of Mercurial
diff --git a/tests/test-treemanifest-server.t b/tests/test-treemanifest-server.t
--- a/tests/test-treemanifest-server.t
+++ b/tests/test-treemanifest-server.t
@@ -120,10 +120,7 @@
   [255]
 
 Test pushing only trees with commit hooks
-  $ cat >> .hg/hgrc <<EOF
-  > [treemanifest]
-  > sendflat=False
-  > EOF
+TODO: change this to create a treeonly commit and try to push it
   $ hg push --to mybook
   pushing to ssh://user@dummy/master
   searching for changes
diff --git a/tests/test-treemanifest-treeonly.t b/tests/test-treemanifest-treeonly.t
--- a/tests/test-treemanifest-treeonly.t
+++ b/tests/test-treemanifest-treeonly.t
@@ -94,7 +94,6 @@
   $ cat >> .hg/hgrc <<EOF
   > [treemanifest]
   > treeonly=True
-  > sendflat=False
   > EOF
 
 Make a local tree-only draft commit
diff --git a/treemanifest/__init__.py b/treemanifest/__init__.py
--- a/treemanifest/__init__.py
+++ b/treemanifest/__init__.py
@@ -56,12 +56,6 @@
    repackstartrev = 0
    repackendrev = 1000
 
-Setting `treemanifest.sendflat` to False will stop flat manifests from being
-sent as part of changegroups during push. It defaults to True.
-
-   [treemanifest]
-   sendflat = True
-
 Setting `treemanifest.treeonly` to True will force all manifest reads to use the
 tree format. This is useful in the final stages of a migration to treemanifest
 to prevent accesses of flat manifests.
@@ -1050,7 +1044,7 @@
 
         # Treemanifest servers don't accept tree directly. They must go through
         # pushrebase, which uses it's own part type and handler.
-        if op.repo.svfs.treemanifestserver:
+        if repo.svfs.treemanifestserver:
             return
 
         if part.params.get('cache', 'False') == 'True':