diff --git a/firecrown/likelihood/source.py b/firecrown/likelihood/source.py
index fab7aff6..72d169b0 100644
--- a/firecrown/likelihood/source.py
+++ b/firecrown/likelihood/source.py
@@ -6,7 +6,7 @@
 from dataclasses import dataclass, replace
 from typing import Generic, Sequence, TypeVar, final, Annotated, Literal
 
-from pydantic import BaseModel, ConfigDict, Field, PrivateAttr
+from pydantic import BaseModel, ConfigDict, Field
 import numpy as np
 import numpy.typing as npt
 import pyccl
@@ -250,6 +250,10 @@ def apply(self, tools: ModelingTools, tracer_arg: _SourceGalaxyArgsT):
         )
 
 
+class PhotoZShift(SourceGalaxyPhotoZShift):
+    """Photo-z shift systematic."""
+
+
 class PhotoZShiftFactory(BaseModel):
     """Factory class for PhotoZShift objects."""