diff --git a/pkgs/development/python-modules/python-smarttub/default.nix b/pkgs/development/python-modules/python-smarttub/default.nix
index 1b1deba78fac..ee7774654524 100644
--- a/pkgs/development/python-modules/python-smarttub/default.nix
+++ b/pkgs/development/python-modules/python-smarttub/default.nix
@@ -38,6 +38,10 @@ buildPythonPackage rec {
     pytestCheckHook
   ];
 
+  pytestFlagsArray = [
+    "--asyncio-mode=legacy"
+  ];
+
   postPatch = ''
     substituteInPlace setup.py \
       --replace "pyjwt~=2.1.0" "pyjwt>=2.1.0"