diff --git a/pyproject.toml b/pyproject.toml
index c834e20..6e0a9d6 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -36,6 +36,7 @@ name = "ecleankernel"
 
 [tool.flit.sdist]
 include = [
+    "COPYING",
     "tox.ini",
     "test/*.py",
 ]