diff --git a/requirements-dev.txt b/requirements-dev.txt
index 4dc2302..2666ea6 100644
--- a/requirements-dev.txt
+++ b/requirements-dev.txt
@@ -2,11 +2,13 @@
 bumpversion==0.5.3
 django-oauth-toolkit==1.0.0
 djangorestframework==3.8.2
-flake8==3.5.0
-isort==4.3.4
+flake8==3.7.8
+isort==4.3.21
 mkdocs==1.0.4
 mock==2.0.0
 model-mommy==1.6.0
 pytest-cov==2.6.0
 pytest-django==3.4.3
-pytest==3.8.2
+pytest==3.8.2; python_version == '2.7'
+pytest==4.6.6; python_version == '3.4'
+pytest==5.2.1; python_version > '3.4'