diff --git a/python/tests/test_lowlevel.py b/python/tests/test_lowlevel.py
index c33f159deb..5e5c5b2272 100644
--- a/python/tests/test_lowlevel.py
+++ b/python/tests/test_lowlevel.py
@@ -1496,6 +1496,13 @@ def test_time_units(self):
             ts.load_tables(tables)
             assert ts.get_time_units() == value
 
+    def test_extend_edges_bad_args(self):
+        ts1 = self.get_example_tree_sequence(10)
+        with pytest.raises(TypeError):
+            ts1.extend_edges()
+        with pytest.raises(TypeError, match="as an int"):
+            ts1.extend_edges("sdf")
+
     def test_kc_distance_errors(self):
         ts1 = self.get_example_tree_sequence(10)
         with pytest.raises(TypeError):