diff --git a/cosipy/image_deconvolution/deconvolution_algorithm_base.py b/cosipy/image_deconvolution/deconvolution_algorithm_base.py
index 4947fad0..63d6a2f5 100644
--- a/cosipy/image_deconvolution/deconvolution_algorithm_base.py
+++ b/cosipy/image_deconvolution/deconvolution_algorithm_base.py
@@ -56,7 +56,11 @@ def __init__(self, initial_model, dataset, mask, parameter):
         logger.debug(f'dict_bkg_norm: {self.dict_bkg_norm}')
         logger.debug(f'dict_dataset_indexlist_for_bkg_models: {self.dict_dataset_indexlist_for_bkg_models}')
 
-        self.minimum_flux = parameter.get('minimum_flux:value', 0.0) * u.Unit(parameter.get('minimum_flux:unit', initial_model.unit))
+        self.minimum_flux = parameter.get('minimum_flux:value', 0.0)
+
+        minimum_flux_unit = parameter.get('minimum_flux:unit', initial_model.unit)
+        if minimum_flux_unit is not None:
+            self.minimum_flux = self.minimum_flux*u.Unit(minimum_flux_unit)
 
         # parameters of the iteration
         self.iteration_count = 0
diff --git a/cosipy/image_deconvolution/model_base.py b/cosipy/image_deconvolution/model_base.py
index 9a55a345..4b7ab9f4 100644
--- a/cosipy/image_deconvolution/model_base.py
+++ b/cosipy/image_deconvolution/model_base.py
@@ -62,7 +62,7 @@ def mask_pixels(self, mask, fill_value = 0):
         fill_value: float or :py:class:`astropy.units.quantity.Quantity`
         """
 
-        if not isinstance(fill_value, u.quantity.Quantity):
+        if not isinstance(fill_value, u.quantity.Quantity) and self.unit is not None:
             fill_value *= self.contents.unit
 
         model_new = copy.deepcopy(self)