diff --git a/tests/requirements.txt b/tests/requirements.txt
index d633271..c3ee05b 100644
--- a/tests/requirements.txt
+++ b/tests/requirements.txt
@@ -1,4 +1,4 @@
 # those are the additional packages required to run the tests
 six
-pyfakefs
+pyfakefs==3.3
 ddt