diff --git a/requirements.txt b/requirements.txt
index cd5124636aa40eaa523f5c8d946d5729cb73dc3c..31ace930b87e4501ae372daf191c05dd97bf6f23 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -17,7 +17,7 @@ toolz==0.10.0  # for dask
 cloudpickle==1.2.2  # for dask
 cython==0.29.15
 pyshp==2.1.0
-six==1.14.0
+six==1.11.0
 pyproj==2.4.2.post1
 shapely==1.7.0
 Cartopy==0.17.0