diff --git a/extensions/transformiix/source/xpath/nsXPathEvaluator.cpp b/extensions/transformiix/source/xpath/nsXPathEvaluator.cpp
index e46a2c3977a..01fa66d66c6 100644
--- a/extensions/transformiix/source/xpath/nsXPathEvaluator.cpp
+++ b/extensions/transformiix/source/xpath/nsXPathEvaluator.cpp
@@ -50,6 +50,7 @@
 #include "nsDOMError.h"
 #include "txURIUtils.h"
 #include "nsIHTMLDocument.h"
+#include "nsIDOMDocument.h"
 
 extern nsINameSpaceManager* gTxNameSpaceManager;