diff --git a/LoopStructural/modelling/core/geological_model.py b/LoopStructural/modelling/core/geological_model.py
index 7caa3435d..c13cc5128 100644
--- a/LoopStructural/modelling/core/geological_model.py
+++ b/LoopStructural/modelling/core/geological_model.py
@@ -579,6 +579,7 @@ def get_interpolator(self, interpolatortype='FDI', nelements=1e4,
             # number of steps is the length of the box / step vector
             nsteps = np.ceil((bb[1, :] - bb[0, :]) / step_vector).astype(int)
             if np.any(np.less(nsteps, 3)):
+                axis_labels = ['x','y','z']
                 for i in range(3):
                     if nsteps[i] < 3:
                         logger.error("Number of steps in direction {} is too small, try increasing nelements".format(axis_labels[i]))