diff --git a/rebound/tests/test_boundary.py b/rebound/tests/test_boundary.py
index c80d392bd..7c653fe65 100644
--- a/rebound/tests/test_boundary.py
+++ b/rebound/tests/test_boundary.py
@@ -4,20 +4,22 @@
 class TestBoundary(unittest.TestCase):
     
     def test_open(self):
-        sim = rebound.Simulation()
-        sim.boundary = "open"
-        sim.configure_box(10.)
-        sim.add(m=0.1,x=1., vx=5.0)
-        sim.add(m=0.1,x=-1., vx=-5.0)
-        sim.add(m=0.1,y=1., vx=6.0)
-        sim.add(m=0.1,x=-1., y=-1., vx=-3., vy=-3.)
-        sim.add(m=0.1,z=1., vz=5.0)
-        sim.add(m=0.1,z=-1., vz=-5.0)
-        self.assertEqual(sim.N,6)
-        sim.integrate(1.)
-        self.assertEqual(sim.N,1)
-        with self.assertRaises(rebound.NoParticles):
-            sim.integrate(2.)
+        for gravity in ["basic", "tree"]:
+            sim = rebound.Simulation()
+            sim.boundary = "open"
+            sim.gravity  = gravity
+            sim.configure_box(10.)
+            sim.add(m=0.1,x=1., vx=5.0)
+            sim.add(m=0.1,x=-1., vx=-5.0)
+            sim.add(m=0.1,y=1., vx=6.0)
+            sim.add(m=0.1,x=-1., y=-1., vx=-3., vy=-3.)
+            sim.add(m=0.1,z=1., vz=5.0)
+            sim.add(m=0.1,z=-1., vz=-5.0)
+            self.assertEqual(sim.N,6)
+            sim.integrate(1.)
+            self.assertEqual(sim.N,1)
+            with self.assertRaises(rebound.NoParticles):
+                sim.integrate(2.)
     
     def test_periodic(self):
         sim = rebound.Simulation()