diff --git a/pkgs/development/python-modules/pypck/default.nix b/pkgs/development/python-modules/pypck/default.nix
index 6fe6e016d1cd..c1996ae402a1 100644
--- a/pkgs/development/python-modules/pypck/default.nix
+++ b/pkgs/development/python-modules/pypck/default.nix
@@ -28,6 +28,10 @@ buildPythonPackage rec {
     pytestCheckHook
   ];
 
+  pytestFlagsArray = [
+    "--asyncio-mode=legacy"
+  ];
+
   disabledTests = lib.optionals stdenv.isDarwin [
     "test_connection_lost"
   ];