1 files changed, 1 insertions, 1 deletions

diff --git a/setup.py b/setup.py
index a09eda0..f80264e 100644
--- a/setup.py
+++ b/setup.py
@@ -20,7 +20,7 @@ setup(
     packages=find_packages(),
     install_requires=[
         'pyzmq==18.1.0',
-        'six==1.14.0',
+        'six>=1.14,<2',
         'monotonic==0.4',
         'croniter==0.3.10',
         'future==0.15.2',