diff --git a/requirements.txt b/requirements.txt
index c976cef..53768c6 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -1,6 +1,6 @@
 # GRPC Python setup requirements
 coverage>=4.0
-cython>=0.23
+cython>=0.27
 enum34>=1.0.4
 futures>=2.2.0
 protobuf>=3.5.0.post1