diff --git a/tangos/core/timestep.py b/tangos/core/timestep.py
index 7c28102d..d45bd21f 100644
--- a/tangos/core/timestep.py
+++ b/tangos/core/timestep.py
@@ -76,8 +76,12 @@ def __getitem__(self, halo_identifier):
 
     @property
     def path(self):
-        with Session.object_session(self).no_autoflush:
+        sess = Session.object_session(self)
+        if sess is None:
             return self.simulation.path+"/"+self.extension
+        else:
+            with sess.no_autoflush:
+                return self.simulation.path+"/"+self.extension
 
     @property
     def redshift_cascade(self):
diff --git a/tests/test_timestep.py b/tests/test_timestep.py
new file mode 100644
index 00000000..e9dc8429
--- /dev/null
+++ b/tests/test_timestep.py
@@ -0,0 +1,9 @@
+import tangos
+from tangos import testing
+
+def setup_module():
+    testing.init_blank_db_for_testing()
+def test_timestep_formatter():
+    sim = tangos.core.Simulation('test_sim')
+    ts = tangos.core.TimeStep(sim, "test_timestep")
+    assert ts.path=="test_sim/test_timestep"
\ No newline at end of file