diff --git a/pkgs/development/python-modules/curio/default.nix b/pkgs/development/python-modules/curio/default.nix
index 65d225dc377..b60025a91b0 100644
--- a/pkgs/development/python-modules/curio/default.nix
+++ b/pkgs/development/python-modules/curio/default.nix
@@ -22,6 +22,8 @@ buildPythonPackage rec {
   # test_aside_basic times out,
   # test_aside_cancel fails because modifies PYTHONPATH and cant find pytest
   checkPhase = ''
+    # __pycache__ was packaged accidentally, https://github.com/dabeaz/curio/issues/301
+    rm -r tests/__pycache__
     pytest --deselect tests/test_task.py::test_aside_basic --deselect tests/test_task.py::test_aside_cancel
   '';