diff --git a/requirements.txt b/requirements.txt
index 0fe3d7e..c864d4c 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -6,6 +6,7 @@ funcy==1.11
 lenses==0.5.0
 hypothesis==4.5.7
 parsimonious==0.8.1
+pytest==4.2.0
 pytest==3.2.3
 pytest-cov==2.6.1
 pytest-flake8==1.0.4