diff --git a/requirements-tests.txt b/requirements-tests.txt
index ed9f9cc..9660aba 100644
--- a/requirements-tests.txt
+++ b/requirements-tests.txt
@@ -1 +1 @@
-coverage
\ No newline at end of file
+coverage==4.5.1
\ No newline at end of file
diff --git a/requirements.txt b/requirements.txt
index 27db988..4a4f95b 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -1,3 +1,3 @@
-pytz
-dataclasses
-bitstruct
+pytz==2018.5
+dataclasses==0.6
+bitstruct==3.9.0