diff --git a/requirements.txt b/requirements.txt
index b6a124017..112715742 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -4,4 +4,4 @@ numpy>=1.19
 numba>=0.51
 scipy>=1.5.1
 scikit_learn>=0.20.0
-six
\ No newline at end of file
+six>=1.4.0,<=1.16.0