diff --git a/tests/qtest/device-introspect-test.c b/tests/qtest/device-introspect-test.c
index 9abb5ec889..d68b7856a7 100644
--- a/tests/qtest/device-introspect-test.c
+++ b/tests/qtest/device-introspect-test.c
@@ -105,14 +105,9 @@ static void test_one_device(QTestState *qts, const char *type)
 {
     QDict *resp;
     char *help;
-    char *qom_tree_start, *qom_tree_end;
-    char *qtree_start, *qtree_end;
 
     g_test_message("Testing device '%s'", type);
 
-    qom_tree_start = qtest_hmp(qts, "info qom-tree");
-    qtree_start = qtest_hmp(qts, "info qtree");
-
     resp = qtest_qmp(qts, "{'execute': 'device-list-properties',"
                           " 'arguments': {'typename': %s}}",
                type);
@@ -120,21 +115,6 @@ static void test_one_device(QTestState *qts, const char *type)
 
     help = qtest_hmp(qts, "device_add \"%s,help\"", type);
     g_free(help);
-
-    /*
-     * Some devices leave dangling pointers in QOM behind.
-     * "info qom-tree" or "info qtree" have a good chance at crashing then.
-     * Also make sure that the tree did not change.
-     */
-    qom_tree_end = qtest_hmp(qts, "info qom-tree");
-    g_assert_cmpstr(qom_tree_start, ==, qom_tree_end);
-    g_free(qom_tree_start);
-    g_free(qom_tree_end);
-
-    qtree_end = qtest_hmp(qts, "info qtree");
-    g_assert_cmpstr(qtree_start, ==, qtree_end);
-    g_free(qtree_start);
-    g_free(qtree_end);
 }
 
 static void test_device_intro_list(void)
@@ -213,16 +193,38 @@ static void test_qom_list_fields(void)
 static void test_device_intro_none(void)
 {
     QTestState *qts = qtest_init(common_args);
+    g_autofree char *qom_tree_start = qtest_hmp(qts, "info qom-tree");
+    g_autofree char *qom_tree_end = NULL;
+    g_autofree char *qtree_start = qtest_hmp(qts, "info qtree");
+    g_autofree char *qtree_end = NULL;
 
     test_one_device(qts, "nonexistent");
+
+    /* Make sure that really nothing changed in the trees */
+    qom_tree_end = qtest_hmp(qts, "info qom-tree");
+    g_assert_cmpstr(qom_tree_start, ==, qom_tree_end);
+    qtree_end = qtest_hmp(qts, "info qtree");
+    g_assert_cmpstr(qtree_start, ==, qtree_end);
+
     qtest_quit(qts);
 }
 
 static void test_device_intro_abstract(void)
 {
     QTestState *qts = qtest_init(common_args);
+    g_autofree char *qom_tree_start = qtest_hmp(qts, "info qom-tree");
+    g_autofree char *qom_tree_end = NULL;
+    g_autofree char *qtree_start = qtest_hmp(qts, "info qtree");
+    g_autofree char *qtree_end = NULL;
 
     test_one_device(qts, "device");
+
+    /* Make sure that really nothing changed in the trees */
+    qom_tree_end = qtest_hmp(qts, "info qom-tree");
+    g_assert_cmpstr(qom_tree_start, ==, qom_tree_end);
+    qtree_end = qtest_hmp(qts, "info qtree");
+    g_assert_cmpstr(qtree_start, ==, qtree_end);
+
     qtest_quit(qts);
 }
 
@@ -231,9 +233,12 @@ static void test_device_intro_concrete(const void *args)
     QList *types;
     QListEntry *entry;
     const char *type;
-    QTestState *qts;
+    QTestState *qts = qtest_init(args);
+    g_autofree char *qom_tree_start = qtest_hmp(qts, "info qom-tree");
+    g_autofree char *qom_tree_end = NULL;
+    g_autofree char *qtree_start = qtest_hmp(qts, "info qtree");
+    g_autofree char *qtree_end = NULL;
 
-    qts = qtest_init(args);
     types = device_type_list(qts, false);
 
     QLIST_FOREACH_ENTRY(types, entry) {
@@ -243,6 +248,17 @@ static void test_device_intro_concrete(const void *args)
         test_one_device(qts, type);
     }
 
+    /*
+     * Some devices leave dangling pointers in QOM behind.
+     * "info qom-tree" or "info qtree" have a good chance at crashing then.
+     * Also make sure that the tree did not change.
+     */
+    qom_tree_end = qtest_hmp(qts, "info qom-tree");
+    g_assert_cmpstr(qom_tree_start, ==, qom_tree_end);
+
+    qtree_end = qtest_hmp(qts, "info qtree");
+    g_assert_cmpstr(qtree_start, ==, qtree_end);
+
     qobject_unref(types);
     qtest_quit(qts);
     g_free((void *)args);