diff --git a/pkgs/development/python-modules/afdko/default.nix b/pkgs/development/python-modules/afdko/default.nix
index f1e3bf0cd56..6371fa804bb 100644
--- a/pkgs/development/python-modules/afdko/default.nix
+++ b/pkgs/development/python-modules/afdko/default.nix
@@ -3,7 +3,7 @@
 , brotli, fontmath, mutatormath, booleanoperations
 , ufoprocessor, ufonormalizer, psautohint, tqdm
 , setuptools_scm
-, pytest
+, pytestCheckHook
 }:
 
 buildPythonPackage rec {
@@ -52,10 +52,18 @@ buildPythonPackage rec {
   # https://github.com/adobe-type-tools/afdko/issues/1163
   # https://github.com/adobe-type-tools/afdko/issues/1216
   doCheck = stdenv.isx86_64;
-  checkInputs = [ pytest ];
-  checkPhase = ''
-    PATH="$PATH:$out/bin" py.test
-  '';
+  checkInputs = [ pytestCheckHook ];
+  preCheck = "export PATH=$PATH:$out/bin";
+  disabledTests = [
+    # Disable slow tests, reduces test time ~25 %
+    "test_report"
+    "test_post_overflow"
+    "test_cjk"
+    "test_extrapolate"
+    "test_filename_without_dir"
+    "test_overwrite"
+    "test_options"
+  ];
 
   meta = with stdenv.lib; {
     description = "Adobe Font Development Kit for OpenType";
diff --git a/pkgs/development/python-modules/psautohint/default.nix b/pkgs/development/python-modules/psautohint/default.nix
index fb9237c8934..61828ddff00 100644
--- a/pkgs/development/python-modules/psautohint/default.nix
+++ b/pkgs/development/python-modules/psautohint/default.nix
@@ -1,7 +1,7 @@
 { lib, buildPythonPackage, fetchFromGitHub, pythonOlder
 , fonttools, lxml, fs
 , setuptools_scm
-, pytest, pytestcov, pytest_xdist, pytest-randomly
+, pytestCheckHook, pytest_5, pytestcov, pytest_xdist
 }:
 
 buildPythonPackage rec {
@@ -11,10 +11,10 @@ buildPythonPackage rec {
   disabled = pythonOlder "3.6";
 
   src = fetchFromGitHub {
-    owner  = "adobe-type-tools";
-    repo   = pname;
+    owner = "adobe-type-tools";
+    repo = pname;
+    rev = "v${version}";
     sha256 = "1s2l54gzn11y07zaggprwif7r3ia244qijjhkbvjdx4jsgc5df8n";
-    rev    = "v${version}";
     fetchSubmodules = true; # data dir for tests
   };
 
@@ -28,8 +28,24 @@ buildPythonPackage rec {
 
   propagatedBuildInputs = [ fonttools lxml fs ];
 
-  checkInputs = [ pytest pytestcov pytest_xdist pytest-randomly ];
-  checkPhase = "pytest tests";
+  checkInputs = [
+    # Override pytestCheckHook to use pytest v5, because some tests fail on pytest >= v6
+    # https://github.com/adobe-type-tools/psautohint/issues/284#issuecomment-742800965
+    # Override might be able to be removed in future, check package dependency pins (coverage.yml)
+    (pytestCheckHook.override{ pytest = pytest_5; })
+    pytestcov
+    pytest_xdist
+  ];
+  disabledTests = [
+    # Slow tests, reduces test time from ~5 mins to ~30s
+    "test_mmufo"
+    "test_flex_ufo"
+    "test_ufo"
+    "test_flex_otf"
+    "test_multi_outpath"
+    "test_mmhint"
+    "test_otf"
+  ];
 
   meta = with lib; {
     description = "Script to normalize the XML and other data inside of a UFO";