diff --git a/requirements.txt b/requirements.txt
index 1b26122..97d1aa2 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -6,4 +6,4 @@ grpcio==1.8.4
 grpcio-tools==1.12.1
 nose==1.3.7
 protobuf==3.5.2
-six==1.11.0
+six==1.15.0