diff --git a/requirements/tests.txt b/requirements/tests.txt
index 3ecc996..a93790a 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==3.8.2
+pytest-xdist==1.23.2  # for --boxed
+hypothesis==3.74.3
+numpy==1.15.2