diff --git a/widget/public/nsITreeDataModel.h b/widget/public/nsITreeDataModel.h
index be674e92b661..767766c417bd 100644
--- a/widget/public/nsITreeDataModel.h
+++ b/widget/public/nsITreeDataModel.h
@@ -30,7 +30,7 @@ class nsITreeItem;
 #define NS_ITREEDATAMODEL_IID \
 { 0x728d90c2, 0x5b2a, 0x11d2, { 0x96, 0xed, 0x0, 0x10, 0x4b, 0x7b, 0x7d, 0xeb } }
 
-class nsITreeDataModel : public nsIDataModel
+class nsITreeDataModel : public nsISupports
 {
 
 public:
diff --git a/widget/public/nsITreeItem.h b/widget/public/nsITreeItem.h
index 839074af41ce..a3ee5e9769c6 100644
--- a/widget/public/nsITreeItem.h
+++ b/widget/public/nsITreeItem.h
@@ -30,7 +30,7 @@ class nsIImageGroup;
 #define NS_ITREEITEM_IID \
 { 0x2fc8fd02, 0x789f, 0x11d2, { 0x96, 0xed, 0x0, 0x10, 0x4b, 0x7b, 0x7d, 0xeb } }
 
-class nsITreeItem : public nsIDMItem
+class nsITreeItem : public nsISupports
 {
 public:
 	// Inspectors