diff --git a/gprMax/cmds_geometry/fractal_box_builder.py b/gprMax/cmds_geometry/fractal_box_builder.py
index bbf2a6ad..b61c404b 100644
--- a/gprMax/cmds_geometry/fractal_box_builder.py
+++ b/gprMax/cmds_geometry/fractal_box_builder.py
@@ -1,13 +1,15 @@
 """Class for fractal box modifications command."""
 from .cmds_geometry import UserObjectGeometry
 from ..exceptions import CmdInputError
-from ..constants import floattype
+from ..config import dtypes
 from ..cython.geometry_primitives import build_voxels_from_array
 from ..cython.geometry_primitives import build_voxels_from_array_mask
 
 import numpy as np
 
 
+floattype = dtypes['float_or_double']
+
 class FractalBoxBuilder(UserObjectGeometry):
     """Internal class for fractal box modifications. This class should be used
     internally only when surface modification have been made to a fractal box"""