diff --git a/ess/fieldmap.py b/ess/fieldmap.py
index 29ee0c5a7aa8be609e91d1cf93b2116b7d460c6b..981a69b794c40122ae0164c4d50be1a455ddce82 100644
--- a/ess/fieldmap.py
+++ b/ess/fieldmap.py
@@ -84,6 +84,7 @@ __all__ = [
     "cut_fieldmap_length",
     "field_on_axis",
     "field_on_axis_from_file",
+    "convert_3d_to_1d",
     "save_to_ascii",
     "batch_convert_to_ascii",
     "unify_grid_size",