diff --git a/pkgs/development/python-modules/mock/2.nix b/pkgs/development/python-modules/mock/2.nix
new file mode 100644
index 00000000000..9ab8de1ba50
--- /dev/null
+++ b/pkgs/development/python-modules/mock/2.nix
@@ -0,0 +1,44 @@
+{ lib
+, buildPythonPackage
+, fetchPypi
+, isPy27
+, funcsigs
+, six
+, pbr
+, python
+, pytest
+}:
+
+buildPythonPackage rec {
+  pname = "mock";
+  version = "3.0.5";
+
+  src = fetchPypi {
+    inherit pname version;
+    sha256 = "83657d894c90d5681d62155c82bda9c1187827525880eda8ff5df4ec813437c3";
+  };
+
+  propagatedBuildInputs = [ six pbr ] ++ lib.optionals isPy27 [ funcsigs ];
+
+  # On PyPy for Python 2.7 in particular, Mock's tests have a known failure.
+  # Mock upstream has a decoration to disable the failing test and make
+  # everything pass, but it is not yet released. The commit:
+  # https://github.com/testing-cabal/mock/commit/73bfd51b7185#diff-354f30a63fb0907d4ad57269548329e3L12
+  #doCheck = !(python.isPyPy && python.isPy27);
+  doCheck = false; # Infinite recursion pytest
+
+  checkPhase = ''
+    ${python.interpreter} -m unittest discover
+  '';
+
+  checkInputs = [
+    pytest
+  ];
+
+  meta = with lib; {
+    description = "Mock objects for Python";
+    homepage = "http://python-mock.sourceforge.net/";
+    license = licenses.bsd2;
+  };
+
+}
\ No newline at end of file
diff --git a/pkgs/development/python-modules/mock/default.nix b/pkgs/development/python-modules/mock/default.nix
index 84c25658b06..e905add00f5 100644
--- a/pkgs/development/python-modules/mock/default.nix
+++ b/pkgs/development/python-modules/mock/default.nix
@@ -6,6 +6,7 @@
 , six
 , pbr
 , python
+, pytest
 }:
 
 buildPythonPackage rec {
@@ -23,12 +24,17 @@ buildPythonPackage rec {
   # Mock upstream has a decoration to disable the failing test and make
   # everything pass, but it is not yet released. The commit:
   # https://github.com/testing-cabal/mock/commit/73bfd51b7185#diff-354f30a63fb0907d4ad57269548329e3L12
-  doCheck = !(python.isPyPy && python.isPy27);
+  #doCheck = !(python.isPyPy && python.isPy27);
+  doCheck = false; # Infinite recursion pytest
 
   checkPhase = ''
     ${python.interpreter} -m unittest discover
   '';
 
+  checkInputs = [
+    pytest
+  ];
+
   meta = with lib; {
     description = "Mock objects for Python";
     homepage = "http://python-mock.sourceforge.net/";
diff --git a/pkgs/top-level/python-packages.nix b/pkgs/top-level/python-packages.nix
index acf1dd558e9..8b6c9c9a1c7 100644
--- a/pkgs/top-level/python-packages.nix
+++ b/pkgs/top-level/python-packages.nix
@@ -4505,7 +4505,10 @@ in {
 
   editorconfig = callPackage ../development/python-modules/editorconfig { };
 
-  mock = callPackage ../development/python-modules/mock { };
+  mock = if pythonOlder "3.6" then
+    callPackage ../development/python-modules/mock/2.nix { }
+  else
+    callPackage ../development/python-modules/mock { };
 
   mock-open = callPackage ../development/python-modules/mock-open { };