diff --git a/cmd/globals.go b/cmd/globals.go
index 3177edd78..e6a2bda28 100644
--- a/cmd/globals.go
+++ b/cmd/globals.go
@@ -206,8 +206,9 @@ var (
 	// RPC V1 - Initial version
 	// RPC V2 - format.json XL version changed to 2
 	// RPC V3 - format.json XL version changed to 3
+	// RPC V4 - ReadFile() arguments signature changed
 	// Current RPC version
-	globalRPCAPIVersion = RPCVersion{3, 0, 0}
+	globalRPCAPIVersion = RPCVersion{4, 0, 0}
 
 	// Allocated etcd endpoint for config and bucket DNS.
 	globalEtcdClient *etcd.Client