diff --git a/requirements.txt b/requirements.txt
index 10003cd..e3f8575 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -4,9 +4,7 @@
 #
 #    pip-compile
 #
-protobuf==3.15.0
+protobuf==3.18.3
     # via -r requirements.in
 pyhamcrest==2.0.2
     # via -r requirements.in
-six==1.15.0
-    # via protobuf