diff --git a/requirements_dev.txt b/requirements_dev.txt
index 575e527..3f63a0c 100644
--- a/requirements_dev.txt
+++ b/requirements_dev.txt
@@ -8,7 +8,7 @@ coverage
 Sphinx
 cryptography
 PyYAML
-pytest
+pytest==3.4.2
 pytest-runner
 numpy
 tox