diff --git a/include/block/block_int-common.h b/include/block/block_int-common.h
index 95392052c9..10feef9f0c 100644
--- a/include/block/block_int-common.h
+++ b/include/block/block_int-common.h
@@ -122,8 +122,9 @@ struct BlockDriver {
     /*
      * Only make sense for filter drivers, for others must be false.
      * If true, filtered child is bs->backing. Otherwise it's bs->file.
-     * Only two internal filters use bs->backing as filtered child and has this
-     * field set to true: mirror_top and commit_top.
+     * Two internal filters use bs->backing as filtered child and has this
+     * field set to true: mirror_top and commit_top. There also two such test
+     * filters in tests/unit/test-bdrv-graph-mod.c.
      *
      * Never create any more such filters!
      *
diff --git a/tests/unit/test-bdrv-graph-mod.c b/tests/unit/test-bdrv-graph-mod.c
index e2f1355af1..c522591531 100644
--- a/tests/unit/test-bdrv-graph-mod.c
+++ b/tests/unit/test-bdrv-graph-mod.c
@@ -26,6 +26,8 @@
 
 static BlockDriver bdrv_pass_through = {
     .format_name = "pass-through",
+    .is_filter = true,
+    .filtered_child_is_backing = true,
     .bdrv_child_perm = bdrv_default_perms,
 };
 
@@ -57,6 +59,8 @@ static void exclusive_write_perms(BlockDriverState *bs, BdrvChild *c,
 
 static BlockDriver bdrv_exclusive_writer = {
     .format_name = "exclusive-writer",
+    .is_filter = true,
+    .filtered_child_is_backing = true,
     .bdrv_child_perm = exclusive_write_perms,
 };
 
@@ -134,7 +138,7 @@ static void test_update_perm_tree(void)
     blk_insert_bs(root, bs, &error_abort);
 
     bdrv_attach_child(filter, bs, "child", &child_of_bds,
-                      BDRV_CHILD_FILTERED | BDRV_CHILD_PRIMARY, &error_abort);
+                      BDRV_CHILD_DATA, &error_abort);
 
     ret = bdrv_append(filter, bs, NULL);
     g_assert_cmpint(ret, <, 0);
@@ -228,11 +232,14 @@ static void test_parallel_exclusive_write(void)
      */
     bdrv_ref(base);
 
-    bdrv_attach_child(top, fl1, "backing", &child_of_bds, BDRV_CHILD_DATA,
+    bdrv_attach_child(top, fl1, "backing", &child_of_bds,
+                      BDRV_CHILD_FILTERED | BDRV_CHILD_PRIMARY,
                       &error_abort);
-    bdrv_attach_child(fl1, base, "backing", &child_of_bds, BDRV_CHILD_FILTERED,
+    bdrv_attach_child(fl1, base, "backing", &child_of_bds,
+                      BDRV_CHILD_FILTERED | BDRV_CHILD_PRIMARY,
                       &error_abort);
-    bdrv_attach_child(fl2, base, "backing", &child_of_bds, BDRV_CHILD_FILTERED,
+    bdrv_attach_child(fl2, base, "backing", &child_of_bds,
+                      BDRV_CHILD_FILTERED | BDRV_CHILD_PRIMARY,
                       &error_abort);
 
     bdrv_replace_node(fl1, fl2, &error_abort);
@@ -344,9 +351,11 @@ static void test_parallel_perm_update(void)
                               BDRV_CHILD_DATA, &error_abort);
     c_fl2 = bdrv_attach_child(ws, fl2, "second", &child_of_bds,
                               BDRV_CHILD_DATA, &error_abort);
-    bdrv_attach_child(fl1, base, "backing", &child_of_bds, BDRV_CHILD_FILTERED,
+    bdrv_attach_child(fl1, base, "backing", &child_of_bds,
+                      BDRV_CHILD_FILTERED | BDRV_CHILD_PRIMARY,
                       &error_abort);
-    bdrv_attach_child(fl2, base, "backing", &child_of_bds, BDRV_CHILD_FILTERED,
+    bdrv_attach_child(fl2, base, "backing", &child_of_bds,
+                      BDRV_CHILD_FILTERED | BDRV_CHILD_PRIMARY,
                       &error_abort);
 
     /* Select fl1 as first child to be active */
@@ -397,7 +406,8 @@ static void test_append_greedy_filter(void)
     BlockDriverState *base = no_perm_node("base");
     BlockDriverState *fl = exclusive_writer_node("fl1");
 
-    bdrv_attach_child(top, base, "backing", &child_of_bds, BDRV_CHILD_COW,
+    bdrv_attach_child(top, base, "backing", &child_of_bds,
+                      BDRV_CHILD_FILTERED | BDRV_CHILD_PRIMARY,
                       &error_abort);
 
     bdrv_append(fl, base, &error_abort);