diff --git a/sup3r/preprocessing/derivers/base.py b/sup3r/preprocessing/derivers/base.py
index 5c9d3ec2d..3c2ce0675 100644
--- a/sup3r/preprocessing/derivers/base.py
+++ b/sup3r/preprocessing/derivers/base.py
@@ -62,7 +62,7 @@ def __init__(
             :py:meth:`sup3r.preprocessing.derivers.Deriver.do_level_interpolation`
         """  # pylint: disable=line-too-long
         if FeatureRegistry is not None:
-            self.FEATURE_REGISTRY.update(FeatureRegistry)
+            self.FEATURE_REGISTRY = FeatureRegistry
 
         super().__init__(data=data)
         self.interp_kwargs = interp_kwargs