diff --git a/mozilla/content/xml/document/src/nsXMLDocument.h b/mozilla/content/xml/document/src/nsXMLDocument.h
index 9d0d6525364..e015152debb 100644
--- a/mozilla/content/xml/document/src/nsXMLDocument.h
+++ b/mozilla/content/xml/document/src/nsXMLDocument.h
@@ -47,6 +47,7 @@
 #include "nsIHttpEventSink.h"
 #include "nsIDOMXMLDocument.h"
 #include "nsIScriptContext.h"
+#include "nsIHTMLStyleSheet.h"
 
 class nsIParser;
 class nsIDOMNode;