diff --git a/pkgs/development/python-modules/jsonrpc-websocket/default.nix b/pkgs/development/python-modules/jsonrpc-websocket/default.nix
index c3d68f77d859..9bd8ef8a108b 100644
--- a/pkgs/development/python-modules/jsonrpc-websocket/default.nix
+++ b/pkgs/development/python-modules/jsonrpc-websocket/default.nix
@@ -33,6 +33,7 @@ buildPythonPackage rec {
   ];
 
   pytestFlagsArray = [
+    "--asyncio-mode=legacy"
     "tests.py"
   ];