diff --git a/regions/core/attributes.py b/regions/core/attributes.py
index <HASH>..<HASH> 100644
--- a/regions/core/attributes.py
+++ b/regions/core/attributes.py
@@ -13,6 +13,10 @@ import numpy as np
 from .core import PixelRegion, SkyRegion
 from .pixcoord import PixCoord
 
+__all__ = ['RegionAttr', 'ScalarPix', 'OneDPix', 'ScalarLength',
+           'ScalarSky', 'OneDSky', 'QuantityLength',
+           'CompoundRegionPix', 'CompoundRegionSky']
+
 
 class RegionAttr(abc.ABC):
     """Descriptor base class"""
Add __all__ to attributes