diff --git a/setup.py b/setup.py
index 51b97c3..c64074a 100644
--- a/setup.py
+++ b/setup.py
@@ -27,6 +27,7 @@ setup(name="magic-wormhole",
 
       package_dir={"": "src"},
       packages=["wormhole",
+                "wormhole._dilation",
                 "wormhole.cli",
                 "wormhole.test",
                 ],