diff --git a/syntaxnet/requirements.txt b/syntaxnet/requirements.txt
index ea31a15..433c8e4 100644
--- a/syntaxnet/requirements.txt
+++ b/syntaxnet/requirements.txt
@@ -1,5 +1,5 @@
 flask
-protobuf==3.3.0
+protobuf==3.18.3
 autograd==1.1.13
 mock
 asciitree