diff --git a/runtime/syntax/proto.vim b/runtime/syntax/proto.vim
index 4d6a77e..4615e0c 100644
--- a/runtime/syntax/proto.vim
+++ b/runtime/syntax/proto.vim
@@ -22,9 +22,8 @@
 "
 " http://code.google.com/p/protobuf/
 
-if version < 600
-  syntax clear
-elseif exists("b:current_syntax")
+" quit when a syntax file was already loaded
+if exists("b:current_syntax")
   finish
 endif