diff --git a/csiborgtools/flow/flow_model.py b/csiborgtools/flow/flow_model.py
index 731f188..1e8c2b6 100644
--- a/csiborgtools/flow/flow_model.py
+++ b/csiborgtools/flow/flow_model.py
@@ -599,7 +599,7 @@ def sample_simple(e_mu_min, e_mu_max, dmu_min, dmu_max, alpha_min, alpha_max,
 
 def sample_calibration(Vext_min, Vext_max, Vmono_min, Vmono_max, beta_min,
                        beta_max, sigma_v_min, sigma_v_max, h_min, h_max,
-                       sample_Vext, sample_Vmono, sample_beta, sample_h):
+                       no_Vext, sample_Vmono, sample_beta, sample_h):
     """Sample the flow calibration."""
     sigma_v = sample("sigma_v", Uniform(sigma_v_min, sigma_v_max))
 
@@ -608,10 +608,10 @@ def sample_calibration(Vext_min, Vext_max, Vmono_min, Vmono_max, beta_min,
     else:
         beta = 1.0
 
-    if sample_Vext:
-        Vext = sample("Vext", Uniform(Vext_min, Vext_max).expand([3]))
-    else:
+    if no_Vext:
         Vext = jnp.zeros(3)
+    else:
+        Vext = sample("Vext", Uniform(Vext_min, Vext_max).expand([3]))
 
     if sample_Vmono:
         Vmono = sample("Vmono", Uniform(Vmono_min, Vmono_max))
diff --git a/csiborgtools/read/paths.py b/csiborgtools/read/paths.py
index 8c0a1c0..83c55f8 100644
--- a/csiborgtools/read/paths.py
+++ b/csiborgtools/read/paths.py
@@ -671,7 +671,7 @@ class Paths:
     def flow_validation(self, fdir, simname, catalogue, inference_method,
                         smooth=None, nsim=None, zcmb_min=None, zcmb_max=None,
                         mag_selection=None,  sample_alpha=False,
-                        sample_beta=False, sample_Vext=None,
+                        sample_beta=False, no_Vext=None,
                         sample_Vmono=False, sample_mag_dipole=False,
                         sample_curvature=False, absolute_calibration=None):
         """Flow validation file path."""
@@ -687,11 +687,11 @@ class Paths:
         fname = f"samples_{simname}_{catalogue}_{inference_method}_"
 
         keys = ["smooth", "nsim", "zcmb_min", "zcmb_max", "mag_selection",
-                "sample_alpha", "sample_beta", "sample_Vext", "sample_Vmono",
+                "sample_alpha", "sample_beta", "no_Vext", "sample_Vmono",
                 "sample_mag_dipole", "sample_curvature",
                 "absolute_calibration"]
         values = [smooth, nsim, zcmb_min, zcmb_max, mag_selection,
-                  sample_alpha, sample_beta, sample_Vext, sample_Vmono,
+                  sample_alpha, sample_beta, no_Vext, sample_Vmono,
                   sample_mag_dipole, sample_curvature, absolute_calibration]
 
         for key, value in zip(keys, values):
diff --git a/scripts/flow/flow_validation.py b/scripts/flow/flow_validation.py
index 36889be..7c015f1 100644
--- a/scripts/flow/flow_validation.py
+++ b/scripts/flow/flow_validation.py
@@ -298,7 +298,7 @@ if __name__ == "__main__":
     mag_selection = None
     sample_alpha = False if "IndranilVoid_" in ARGS.simname else True
     sample_beta = None
-    sample_Vext = None
+    no_Vext = True
     sample_Vmono = False
     sample_mag_dipole = False
     absolute_calibration = None
@@ -313,7 +313,7 @@ if __name__ == "__main__":
                     "mag_selection": mag_selection,
                     "sample_alpha": sample_alpha,
                     "sample_beta": sample_beta,
-                    "sample_Vext": sample_Vext,
+                    "no_Vext": no_Vext,
                     "sample_Vmono": sample_Vmono,
                     "sample_mag_dipole": sample_mag_dipole,
                     "absolute_calibration": absolute_calibration,
@@ -356,7 +356,7 @@ if __name__ == "__main__":
                                "beta_min": -10.0, "beta_max": 10.0,
                                "sigma_v_min": 1.0, "sigma_v_max": 750.,
                                "h_min": 0.01, "h_max": 5.0,
-                               "sample_Vext": True if sample_Vext is None else sample_Vext,  # noqa
+                               "no_Vext": False if no_Vext is None else no_Vext,  # noqa
                                "sample_Vmono": sample_Vmono,
                                "sample_beta": sample_beta,
                                "sample_h": sample_h,