diff --git a/grpc.go b/grpc.go
index bd1b701..b06b836 100644
--- a/grpc.go
+++ b/grpc.go
@@ -26,7 +26,7 @@ import (
 )
 
 const (
-	DefaultContentType = "application/grpc+proto"
+	DefaultContentType = "application/grpc"
 )
 
 type grpcClient struct {