Compile the attached testcase, press 'a' in the entry, the autocompletion treeview will only show three rows (there's three lines in the model), but only the first one will have something in it.

git bisect says the commit that broke this is:

commit af73305d37fa185308995b99d8332d9eea2ffe68
Author: Kristian Rietveld <kris@gtk.org>
Date:   Tue Sep 1 17:51:19 2009 +0200

    Marking nodes invisible after pulling in the root level is wrong

diff --git a/gtk/gtktreemodelfilter.c b/gtk/gtktreemodelfilter.c
index 0d982b2..49020af 100644
--- a/gtk/gtktreemodelfilter.c
+++ b/gtk/gtktreemodelfilter.c
@@ -1284,13 +1284,6 @@ gtk_tree_model_filter_row_changed (GtkTreeModel *c_model,
       gtk_tree_model_filter_build_level (filter, NULL, NULL, FALSE);

       root = FILTER_LEVEL (filter->priv->root);
-
-      if (root)
-        {
-          for (i = 0; i < root->array->len; i++)
-            g_array_index (root->array, FilterElt, i).visible = FALSE;
-          root->visible_nodes = 0;
-        }
     }

   gtk_tree_model_filter_increment_stamp (filter);