diff --git a/pyproject.toml b/pyproject.toml
index 4bbafc23..5157ab88 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -78,7 +78,13 @@ test = [
 ]
 
 [project.entry-points."dask.sizeof"]
-awkward = "dask_awkward.sizeof:register"
+awkward = "dask_awkward_sizeof:register"
+
+[tool.hatch.build.targets.sdist.force-include]
+"../src/dask_awkward_sizeof" = "src/dask_awkward_sizeof"
+
+[tool.hatch.build.targets.wheel]
+packages = ["src/dask_awkward", "src/dask_awkward_sizeof"]
 
 [project.entry-points."awkward.pickle.reduce"]
 dask_awkward = "dask_awkward.pickle:plugin"
diff --git a/src/dask_awkward/sizeof.py b/src/dask_awkward_sizeof/__init__.py
similarity index 100%
rename from src/dask_awkward/sizeof.py
rename to src/dask_awkward_sizeof/__init__.py