diff --git a/gprMax/fields_outputs.py b/gprMax/fields_outputs.py
index 0d1891e8..9f0d8da5 100644
--- a/gprMax/fields_outputs.py
+++ b/gprMax/fields_outputs.py
@@ -22,6 +22,7 @@ from string import Template
 import h5py
 
 from ._version import __version__
+from .grid import Ix, Iy, Iz
 
 logger = logging.getLogger(__name__)