diff --git a/nes/nc_projections/points_nes.py b/nes/nc_projections/points_nes.py
index e0bec7f985982a8cd0d721fba789b44a44ed4066..8f386991f8852d9f974175cb74d3a40fa9cabff4 100644
--- a/nes/nc_projections/points_nes.py
+++ b/nes/nc_projections/points_nes.py
@@ -392,7 +392,7 @@ class PointsNes(Nes):
                         try:
                             var_dict['data'] = var_dict['data'].to_numpy()
                         except AttributeError:
-                            raise AttributeError("Data for variable {0} must be a numpy array (np.ndarray or np.generic)".var_name)
+                            raise AttributeError("Data for variable {0} must be a numpy array (np.ndarray or np.generic)".format(var_name))
 
                     # Set dtype
                     if 'dtype' in var_dict.keys():