diff --git a/cc/builder.go b/cc/builder.go
index b813783..60aad0b 100644
--- a/cc/builder.go
+++ b/cc/builder.go
@@ -173,6 +173,7 @@
 	ldFlags     string
 	libFlags    string
 	yaccFlags   string
+	protoFlags  string
 	toolchain   config.Toolchain
 	clang       bool