diff --git a/requirements/tests.txt b/requirements/tests.txt
index 3ecc996..6765181 100644
--- a/requirements/tests.txt
+++ b/requirements/tests.txt
@@ -1,5 +1,5 @@
 # latest version to validate behavior on pure python env
-pytest
-pytest-xdist  # for --boxed
-hypothesis
-numpy
+pytest==4.5.0
+pytest-xdist==1.28.0  # for --boxed
+hypothesis==4.23.6
+numpy==1.16.3