diff --git a/psiflow/sampling/sampling.py b/psiflow/sampling/sampling.py
index b0f8727..ec5ff62 100644
--- a/psiflow/sampling/sampling.py
+++ b/psiflow/sampling/sampling.py
@@ -121,20 +121,14 @@ def setup_motion(walker: Walker, fix_com: bool) -> ET.Element:
         else:
             dynamics.append(thermostat)
     elif walker.npt:
-        if walker.volume_constrained:
-            mode = "nst"
-        else:
-            mode = "npt"
+        mode = "npt"
         dynamics = ET.Element("dynamics", mode=mode)
         dynamics.append(timestep_element)
         if walker.pimd:
             dynamics.append(thermostat_pimd)
         else:
             dynamics.append(thermostat)
-        if walker.volume_constrained:
-            mode = "anisotropic"
-        else:
-            mode = "flexible"
+        mode = "flexible"
         barostat = ET.Element("barostat", mode=mode)
         tau = ET.Element("tau", units="femtosecond")
         tau.text = "200"
diff --git a/psiflow/sampling/walker.py b/psiflow/sampling/walker.py
index 8db0454..45cb350 100644
--- a/psiflow/sampling/walker.py
+++ b/psiflow/sampling/walker.py
@@ -49,7 +49,6 @@ class Walker:
     state: Union[Geometry, AppFuture, None]
     temperature: Optional[float]
     pressure: Optional[float]
-    volume_constrained: bool
     nbeads: int
     timestep: float
     coupling: Optional[Coupling]
@@ -63,7 +62,6 @@ def __init__(
         state: Union[Geometry, AppFuture, None] = None,
         temperature: Optional[float] = 300,
         pressure: Optional[float] = None,
-        volume_constrained: bool = False,
         nbeads: int = 1,
         timestep: float = 0.5,
         metadynamics: Optional[Metadynamics] = None,
@@ -82,7 +80,6 @@ def __init__(
 
         self.temperature = temperature
         self.pressure = pressure
-        self.volume_constrained = volume_constrained
         self.nbeads = nbeads
         self.timestep = timestep
 
diff --git a/tests/test_sampling.py b/tests/test_sampling.py
index 219d87d..ab47170 100644
--- a/tests/test_sampling.py
+++ b/tests/test_sampling.py
@@ -295,25 +295,6 @@ def test_npt(dataset):
         output.state.result().cell,
     )
 
-    walker = Walker(
-        dataset[0],
-        einstein,
-        temperature=600,
-        pressure=0,
-        volume_constrained=True,
-    )
-    output = sample([walker], steps=30)[0]
-    # cell should have changed, but not the volume
-    assert not np.allclose(
-        walker.start.result().cell,
-        output.state.result().cell,
-    )
-    # volume actually does change with barostat mode='nst' (?)
-    # assert np.allclose(
-    #     np.linalg.det(walker.start.result().cell),
-    #     np.linalg.det(output.state.result().cell),
-    # )
-
 
 def test_reset(dataset):
     einstein = EinsteinCrystal(dataset[0], force_constant=0.1)