diff --git a/src/build123d/topology.py b/src/build123d/topology.py
index 6199bc16..3cf6e8c1 100644
--- a/src/build123d/topology.py
+++ b/src/build123d/topology.py
@@ -2393,7 +2393,9 @@ def filter_by(
         def axis_parallel_predicate(axis: Axis, tolerance: float):
             def pred(shape: Shape):
                 if shape.is_planar_face:
-                    assert shape.wrapped is not None and isinstance(shape, Face)
+                    assert shape.wrapped is not None and isinstance(
+                        shape.wrapped, TopoDS_Face
+                    )
                     gp_pnt = gp_Pnt()
                     surface_normal = gp_Vec()
                     u_val, _, v_val, _ = BRepTools.UVBounds_s(shape.wrapped)
@@ -2428,7 +2430,9 @@ def plane_parallel_predicate(plane: Plane, tolerance: float):
 
             def pred(shape: Shape):
                 if shape.is_planar_face:
-                    assert shape.wrapped is not None and isinstance(shape, Face)
+                    assert shape.wrapped is not None and isinstance(
+                        shape.wrapped, TopoDS_Face
+                    )
                     gp_pnt: gp_Pnt = gp_Pnt()
                     surface_normal: gp_Vec = gp_Vec()
                     u_val, _, v_val, _ = BRepTools.UVBounds_s(shape.wrapped)