diff --git a/grpc.go b/grpc.go
index 1e328b8..2e485ca 100644
--- a/grpc.go
+++ b/grpc.go
@@ -35,7 +35,7 @@ import (
 )
 
 const (
-	defaultContentType = "application/grpc"
+	defaultContentType = "application/grpc+proto"
 )
 
 /*