diff --git a/pkgs/development/python-modules/requests-mock/default.nix b/pkgs/development/python-modules/requests-mock/default.nix
index 0f159f2a2020..0a3b3d33a087 100644
--- a/pkgs/development/python-modules/requests-mock/default.nix
+++ b/pkgs/development/python-modules/requests-mock/default.nix
@@ -22,6 +22,11 @@ buildPythonPackage rec {
     hash = "sha256-6eEuMztSUVboKjyFLyIBa5FYIg0vR0VN6crop303FAE=";
   };
 
+  postPatch = ''
+    substituteInPlace tests/test_mocker.py \
+      --replace-fail assertEquals assertEqual
+  '';
+
   build-system = [
     setuptools
     setuptools-scm