diff --git a/pkgs/development/python-modules/magic-wormhole-transit-relay/default.nix b/pkgs/development/python-modules/magic-wormhole-transit-relay/default.nix
index 761e7deff0e9..3c3e46f92c0e 100644
--- a/pkgs/development/python-modules/magic-wormhole-transit-relay/default.nix
+++ b/pkgs/development/python-modules/magic-wormhole-transit-relay/default.nix
@@ -2,6 +2,7 @@
   lib,
   buildPythonPackage,
   fetchPypi,
+  fetchpatch,
   setuptools,
   autobahn,
   twisted,
@@ -19,6 +20,15 @@ buildPythonPackage rec {
     hash = "sha256-kS2DXaIbESZsdxEdybXlgAJj/AuY8KF5liJn30GBnow=";
   };
 
+  patches = [
+    # TODO: drop when updating beyond version 0.4.0
+    (fetchpatch {
+      name = "stock-Twisted-testing-reactor-seems-to-work.patch";
+      url = "https://github.com/magic-wormhole/magic-wormhole-transit-relay/commit/3abb80fd5e55bd0ba8ee66278ccf76be5f904622.patch";
+      hash = "sha256-qMaJ58kPWvEfnSZiFzxO6GlkBiyVMsgGDEa1deITZco=";
+    })
+  ];
+
   postPatch = ''
     # Passing the environment to twistd is necessary to preserve Python's site path.
     substituteInPlace src/wormhole_transit_relay/test/test_backpressure.py --replace-fail \