diff --git a/tests/qapi-schema/qapi-schema-test.json b/tests/qapi-schema/qapi-schema-test.json
index c7e6be8..f5c5d37 100644
--- a/tests/qapi-schema/qapi-schema-test.json
+++ b/tests/qapi-schema/qapi-schema-test.json
@@ -34,6 +34,7 @@
   'data': { 'integer': 'int' } }
 
 { 'union': 'UserDefUnion',
+  'base': 'UserDefZero',
   'data': { 'a' : 'UserDefA', 'b' : 'UserDefB' } }
 
 { 'union': 'UserDefAnonUnion',
diff --git a/tests/qapi-schema/qapi-schema-test.out b/tests/qapi-schema/qapi-schema-test.out
index 89e213a..3f51afd 100644
--- a/tests/qapi-schema/qapi-schema-test.out
+++ b/tests/qapi-schema/qapi-schema-test.out
@@ -6,7 +6,7 @@
  OrderedDict([('type', 'UserDefNested'), ('data', OrderedDict([('string0', 'str'), ('dict1', OrderedDict([('string1', 'str'), ('dict2', OrderedDict([('userdef1', 'UserDefOne'), ('string2', 'str')])), ('*dict3', OrderedDict([('userdef2', 'UserDefOne'), ('string3', 'str')]))]))]))]),
  OrderedDict([('type', 'UserDefA'), ('data', OrderedDict([('boolean', 'bool')]))]),
  OrderedDict([('type', 'UserDefB'), ('data', OrderedDict([('integer', 'int')]))]),
- OrderedDict([('union', 'UserDefUnion'), ('data', OrderedDict([('a', 'UserDefA'), ('b', 'UserDefB')]))]),
+ OrderedDict([('union', 'UserDefUnion'), ('base', 'UserDefZero'), ('data', OrderedDict([('a', 'UserDefA'), ('b', 'UserDefB')]))]),
  OrderedDict([('union', 'UserDefAnonUnion'), ('discriminator', OrderedDict()), ('data', OrderedDict([('uda', 'UserDefA'), ('s', 'str'), ('i', 'int')]))]),
  OrderedDict([('union', 'UserDefNativeListUnion'), ('data', OrderedDict([('integer', ['int']), ('s8', ['int8']), ('s16', ['int16']), ('s32', ['int32']), ('s64', ['int64']), ('u8', ['uint8']), ('u16', ['uint16']), ('u32', ['uint32']), ('u64', ['uint64']), ('number', ['number']), ('boolean', ['bool']), ('string', ['str'])]))]),
  OrderedDict([('command', 'user_def_cmd'), ('data', OrderedDict())]),
diff --git a/tests/test-qmp-input-strict.c b/tests/test-qmp-input-strict.c
index 67adc2a..9b99b48 100644
--- a/tests/test-qmp-input-strict.c
+++ b/tests/test-qmp-input-strict.c
@@ -132,7 +132,7 @@ static void test_validate_union(TestInputVisitorData *data,
     Visitor *v;
     Error *errp = NULL;
 
-    v = validate_test_init(data, "{ 'type': 'b', 'data' : { 'integer': 42 } }");
+    v = validate_test_init(data, "{ 'type': 'b', 'integer': 41, 'data' : { 'integer': 42 } }");
 
     visit_type_UserDefUnion(v, &tmp, NULL, &errp);
     g_assert(!errp);
@@ -205,7 +205,7 @@ static void test_validate_fail_union(TestInputVisitorData *data,
     Error *errp = NULL;
     Visitor *v;
 
-    v = validate_test_init(data, "{ 'type': 'b', 'data' : { 'integer': 42 }, 'extra': 'yyy' }");
+    v = validate_test_init(data, "{ 'type': 'b', 'data' : { 'integer': 42 } }");
 
     visit_type_UserDefUnion(v, &tmp, NULL, &errp);
     g_assert(errp);
diff --git a/tests/test-qmp-input-visitor.c b/tests/test-qmp-input-visitor.c
index 9c7bf38..a0607cf 100644
--- a/tests/test-qmp-input-visitor.c
+++ b/tests/test-qmp-input-visitor.c
@@ -293,11 +293,12 @@ static void test_visitor_in_union(TestInputVisitorData *data,
     Error *err = NULL;
     UserDefUnion *tmp;
 
-    v = visitor_input_test_init(data, "{ 'type': 'b', 'data' : { 'integer': 42 } }");
+    v = visitor_input_test_init(data, "{ 'type': 'b', 'integer': 41, 'data' : { 'integer': 42 } }");
 
     visit_type_UserDefUnion(v, &tmp, NULL, &err);
     g_assert(err == NULL);
     g_assert_cmpint(tmp->kind, ==, USER_DEF_UNION_KIND_B);
+    g_assert_cmpint(tmp->integer, ==, 41);
     g_assert_cmpint(tmp->b->integer, ==, 42);
     qapi_free_UserDefUnion(tmp);
 }
diff --git a/tests/test-qmp-output-visitor.c b/tests/test-qmp-output-visitor.c
index 6b29849..c932871 100644
--- a/tests/test-qmp-output-visitor.c
+++ b/tests/test-qmp-output-visitor.c
@@ -416,6 +416,7 @@ static void test_visitor_out_union(TestOutputVisitorData *data,
 
     UserDefUnion *tmp = g_malloc0(sizeof(UserDefUnion));
     tmp->kind = USER_DEF_UNION_KIND_A;
+    tmp->integer = 41;
     tmp->a = g_malloc0(sizeof(UserDefA));
     tmp->a->boolean = true;
 
@@ -427,6 +428,7 @@ static void test_visitor_out_union(TestOutputVisitorData *data,
     qdict = qobject_to_qdict(arg);
 
     g_assert_cmpstr(qdict_get_str(qdict, "type"), ==, "a");
+    g_assert_cmpint(qdict_get_int(qdict, "integer"), ==, 41);
 
     qvalue = qdict_get(qdict, "data");
     g_assert(data != NULL);
