diff --git a/pyproject.toml b/pyproject.toml
index 844bf47..921661c 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -41,6 +41,9 @@ classifiers = [
     "Programming Language :: Python :: 3.9",
     "Topic :: Software Development :: Libraries"
 ]
+include = [
+    {path = "tests", format = "sdist"},
+]
 
 [tool.poetry.dependencies]
 python = "^3.7.0"