diff --git a/gtk/gtktreeview.c b/gtk/gtktreeview.c
index 2c3b00a768..d0baa4576b 100644
--- a/gtk/gtktreeview.c
+++ b/gtk/gtktreeview.c
@@ -8967,7 +8967,7 @@ check_selection_helper (GtkRBTree *tree,
 {
   gint *value = (gint *)data;
 
-  *value = GTK_RBNODE_FLAG_SET (node, GTK_RBNODE_IS_SELECTED);
+  *value |= GTK_RBNODE_FLAG_SET (node, GTK_RBNODE_IS_SELECTED);
 
   if (node->children && !*value)
     _gtk_rbtree_traverse (node->children, node->children->root, G_POST_ORDER, check_selection_helper, data);