diff --git a/xpcom/base/nsError.h b/xpcom/base/nsError.h
index 52f06a5fa916..a6510d68a255 100644
--- a/xpcom/base/nsError.h
+++ b/xpcom/base/nsError.h
@@ -65,6 +65,7 @@ typedef PRUint32 nsresult;
 #define NS_ERROR_MODULE_UCONV      11
 #define NS_ERROR_MODULE_REG        12
 #define NS_ERROR_MODULE_FILES      13
+#define NS_ERROR_MODULE_DOM        14
 
 #define NS_ERROR_MODULE_MAILNEWS   16
 #define NS_ERROR_MODULE_EDITOR     17