diff --git a/git-remote-hg b/git-remote-hg
index 3c79daf..35f469a 100755
--- a/git-remote-hg
+++ b/git-remote-hg
@@ -648,7 +648,10 @@ def do_list(parser):
             print "? refs/heads/branches/%s" % gitref(branch)
 
     for bmark in bmarks:
-        print "? refs/heads/%s" % gitref(bmark)
+        if  bmarks[bmark].hex() == '0' * 40:
+            warn("Ignoring invalid bookmark '%s'", bmark)
+        else:
+            print "? refs/heads/%s" % gitref(bmark)
 
     for tag, node in repo.tagslist():
         if tag == 'tip':
diff --git a/test/main.t b/test/main.t
index b8625ca..22c82f6 100755
--- a/test/main.t
+++ b/test/main.t
@@ -773,4 +773,29 @@ test_expect_success 'remote double failed push' '
 	)
 '
 
+test_expect_success 'clone remote with null bookmark, then push' '
+	test_when_finished "rm -rf gitrepo* hgrepo*" &&
+
+	(
+	hg init hgrepo &&
+	cd hgrepo &&
+	echo a > a &&
+	hg add a &&
+	hg commit -m a &&
+	hg bookmark -r null bookmark
+	) &&
+
+	(
+	git clone "hg::hgrepo" gitrepo &&
+	check gitrepo HEAD a &&
+	cd gitrepo &&
+	git checkout --quiet -b bookmark &&
+	git remote -v &&
+	echo b > b &&
+	git add b &&
+	git commit -m b &&
+	git push origin bookmark
+	)
+'
+
 test_done