diff --git a/runtime/syntax/xml.vim b/runtime/syntax/xml.vim
index 7b503ab..2fd5e1f 100644
--- a/runtime/syntax/xml.vim
+++ b/runtime/syntax/xml.vim
@@ -286,9 +286,11 @@
 
 syn keyword xmlDocTypeKeyword contained DOCTYPE PUBLIC SYSTEM
 syn region  xmlInlineDTD contained matchgroup=xmlDocTypeDecl start="\[" end="]" contains=@xmlDTD
-syn include @xmlDTD <sfile>:p:h/dtd.vim
-unlet b:current_syntax
 
+if exists('g:xml_syntax_folding')
+    syn include @xmlDTD <sfile>:p:h/dtd.vim
+    unlet b:current_syntax
+endif
 
 " synchronizing
 " TODO !!! to be improved !!!