diff --git a/geoapps/inversion/components/models.py b/geoapps/inversion/components/models.py
index ef6f4e74a..3cf0b40bd 100644
--- a/geoapps/inversion/components/models.py
+++ b/geoapps/inversion/components/models.py
@@ -133,8 +133,8 @@ def reference(self) -> np.ndarray | None:
             return mref
 
         if mref is None or (self.is_sigma and all(mref == 0)):
-            mref = self.starting
             self.driver.params.alpha_s = 0.0
+            return self.starting.copy()
 
         ref_model = mref.copy()
         ref_model = np.log(ref_model) if self.is_sigma else ref_model
diff --git a/geoapps/inversion/joint/joint_surveys/driver.py b/geoapps/inversion/joint/joint_surveys/driver.py
index 46aab255b..6e4265377 100644
--- a/geoapps/inversion/joint/joint_surveys/driver.py
+++ b/geoapps/inversion/joint/joint_surveys/driver.py
@@ -98,9 +98,15 @@ def directives(self):
                             )
 
                 self._directives = DirectivesFactory(self)
+                global_model_save = self._directives.save_iteration_model_directive
+                if self.models.is_sigma:
+                    global_model_save.transforms += [
+                        maps.ExpMap(self.inversion_mesh.mesh)
+                    ]
+
                 self._directives.directive_list = (
                     self._directives.inversion_directives
-                    + [self._directives.save_iteration_model_directive]
+                    + [global_model_save]
                     + directives_list
                 )
         return self._directives