diff --git a/hexrd/ui/hexrd_config.py b/hexrd/ui/hexrd_config.py
index 3943ca804..215de8202 100644
--- a/hexrd/ui/hexrd_config.py
+++ b/hexrd/ui/hexrd_config.py
@@ -890,14 +890,18 @@ def raw_masks_dict(self):
 
         return masks_dict
 
-    @property
-    def masked_images_dict(self):
+    def create_masked_images_dict(self, fill_value=0):
         """Get an images dict where masks have been applied"""
         images_dict = self.images_dict
+        have_masks = len(self.visible_masks)
         for det, mask in self.raw_masks_dict.items():
             for name, img in images_dict.items():
+                if (have_masks and
+                        np.issubdtype(type(fill_value), np.floating) and
+                        not np.issubdtype(img.dtype, np.floating)):
+                    img = img.astype(float)
                 if det == name:
-                    img[~mask] = 0
+                    img[~mask] = fill_value
 
         return images_dict