diff --git a/jdaviz/configs/default/plugins/model_fitting/model_fitting.py b/jdaviz/configs/default/plugins/model_fitting/model_fitting.py
index d1cc35d5c8..3d97678d4e 100644
--- a/jdaviz/configs/default/plugins/model_fitting/model_fitting.py
+++ b/jdaviz/configs/default/plugins/model_fitting/model_fitting.py
@@ -982,7 +982,9 @@ def _fit_model_to_cube(self, add_data):
 
         sb_unit = self.app._get_display_unit('sb')
         if spec.flux.unit != sb_unit:
-            spec = spec.with_flux_unit(sb_unit)
+            # ensure specutils has access to jdaviz custom unit equivalencies
+            equivalencies = all_flux_unit_conversion_equivs()
+            spec = spec.with_flux_unit(sb_unit, equivalencies=equivalencies)
 
         snackbar_message = SnackbarMessage(
             "Fitting model to cube...",
diff --git a/jdaviz/utils.py b/jdaviz/utils.py
index 266edeab12..f4ce7b3bd5 100644
--- a/jdaviz/utils.py
+++ b/jdaviz/utils.py
@@ -505,6 +505,7 @@ def _indirect_conversion(values, orig_units, targ_units, eqv,
     elif image_data or (spec_unit and solid_angle_in_spec):
         if not solid_angle_in_targ:
             targ_units /= solid_angle_in_spec
+        solid_angle_in_targ = solid_angle_in_spec
         if ((u.Unit(targ_units) in indirect_units()) or
            (u.Unit(orig_units) in indirect_units())):
             # SB -> Flux -> Flux -> SB