diff --git a/bilby/gw/prior.py b/bilby/gw/prior.py
index 99b971adf4aedbab8912bc390a49420f49450917..8d8f360e3e65f20fc6d7e84a4af93b7d68bb63dc 100644
--- a/bilby/gw/prior.py
+++ b/bilby/gw/prior.py
@@ -553,14 +553,14 @@ class CalibrationPriorDict(PriorDict):
             prior[name] = Gaussian(mu=amplitude_mean_nodes[ii],
                                    sigma=amplitude_sigma_nodes[ii],
                                    name=name, latex_label=latex_label,
-                                   boundary=None)
+                                   boundary='reflective')
         for ii in range(n_nodes):
             name = "recalib_{}_phase_{}".format(label, ii)
             latex_label = "$\\phi^{}_{}$".format(label, ii)
             prior[name] = Gaussian(mu=phase_mean_nodes[ii],
                                    sigma=phase_sigma_nodes[ii],
                                    name=name, latex_label=latex_label,
-                                   boundary=None)
+                                   boundary='reflective')
         for ii in range(n_nodes):
             name = "recalib_{}_frequency_{}".format(label, ii)
             latex_label = "$f^{}_{}$".format(label, ii)
@@ -614,14 +614,14 @@ class CalibrationPriorDict(PriorDict):
             prior[name] = Gaussian(mu=amplitude_mean_nodes[ii],
                                    sigma=amplitude_sigma_nodes[ii],
                                    name=name, latex_label=latex_label,
-                                   boundary=None)
+                                   boundary='reflective')
         for ii in range(n_nodes):
             name = "recalib_{}_phase_{}".format(label, ii)
             latex_label = "$\\phi^{}_{}$".format(label, ii)
             prior[name] = Gaussian(mu=phase_mean_nodes[ii],
                                    sigma=phase_sigma_nodes[ii],
                                    name=name, latex_label=latex_label,
-                                   boundary=None)
+                                   boundary='reflective')
         for ii in range(n_nodes):
             name = "recalib_{}_frequency_{}".format(label, ii)
             latex_label = "$f^{}_{}$".format(label, ii)