diff --git a/scripts/qapi-types.py b/scripts/qapi-types.py
index 914f055..5031c4b 100644
--- a/scripts/qapi-types.py
+++ b/scripts/qapi-types.py
@@ -201,14 +201,21 @@ def generate_union(expr):
     base = expr.get('base')
     discriminator = expr.get('discriminator')
 
+    enum_define = discriminator_find_enum_define(expr)
+    if enum_define:
+        discriminator_type_name = enum_define['enum_name']
+    else:
+        discriminator_type_name = '%sKind' % (name)
+
     ret = mcgen('''
 struct %(name)s
 {
-    %(name)sKind kind;
+    %(discriminator_type_name)s kind;
     union {
         void *data;
 ''',
-                name=name)
+                name=name,
+                discriminator_type_name=discriminator_type_name)
 
     for key in typeinfo:
         ret += mcgen('''
@@ -389,8 +396,11 @@ for expr in exprs:
         fdef.write(generate_enum_lookup(expr['enum'], expr['data']))
     elif expr.has_key('union'):
         ret += generate_fwd_struct(expr['union'], expr['data']) + "\n"
-        ret += generate_enum('%sKind' % expr['union'], expr['data'].keys())
-        fdef.write(generate_enum_lookup('%sKind' % expr['union'], expr['data'].keys()))
+        enum_define = discriminator_find_enum_define(expr)
+        if not enum_define:
+            ret += generate_enum('%sKind' % expr['union'], expr['data'].keys())
+            fdef.write(generate_enum_lookup('%sKind' % expr['union'],
+                                            expr['data'].keys()))
         if expr.get('discriminator') == {}:
             fdef.write(generate_anon_union_qtypes(expr))
     else:
diff --git a/scripts/qapi-visit.py b/scripts/qapi-visit.py
index 787034c..85f17e1 100644
--- a/scripts/qapi-visit.py
+++ b/scripts/qapi-visit.py
@@ -267,10 +267,14 @@ def generate_visit_union(expr):
                                  (key, enum_define["enum_name"]))
                 sys.exit(1)
 
-    # There will always be a discriminator in the C switch code, by default it
-    # is an enum type generated silently as "'%sKind' % (name)"
-    ret = generate_visit_enum('%sKind' % name, members.keys())
-    discriminator_type_name = '%sKind' % (name)
+        # Use the predefined enum type as discriminator
+        ret = ""
+        discriminator_type_name = enum_define['enum_name']
+    else:
+        # There will always be a discriminator in the C switch code, by default it
+        # is an enum type generated silently as "'%sKind' % (name)"
+        ret = generate_visit_enum('%sKind' % name, members.keys())
+        discriminator_type_name = '%sKind' % (name)
 
     if base:
         base_fields = find_struct(base)['data']
@@ -305,11 +309,12 @@ void visit_type_%(name)s(Visitor *m, %(name)s ** obj, const char *name, Error **
 
     pop_indent()
     ret += mcgen('''
-        visit_type_%(name)sKind(m, &(*obj)->kind, "%(type)s", &err);
+        visit_type_%(discriminator_type_name)s(m, &(*obj)->kind, "%(type)s", &err);
         if (!err) {
             switch ((*obj)->kind) {
 ''',
-                 name=name, type="type" if not discriminator else discriminator)
+                 discriminator_type_name=discriminator_type_name,
+                 type="type" if not discriminator else discriminator)
 
     for key in members:
         if not discriminator:
@@ -531,7 +536,11 @@ for expr in exprs:
         ret += generate_visit_list(expr['union'], expr['data'])
         fdef.write(ret)
 
-        ret = generate_decl_enum('%sKind' % expr['union'], expr['data'].keys())
+        enum_define = discriminator_find_enum_define(expr)
+        ret = ""
+        if not enum_define:
+            ret = generate_decl_enum('%sKind' % expr['union'],
+                                     expr['data'].keys())
         ret += generate_declaration(expr['union'], expr['data'])
         fdecl.write(ret)
     elif expr.has_key('enum'):
diff --git a/scripts/qapi.py b/scripts/qapi.py
index f14b31f..462a6ec 100644
--- a/scripts/qapi.py
+++ b/scripts/qapi.py
@@ -172,7 +172,9 @@ def parse_schema(fp):
             add_enum(expr['enum'], expr['data'])
         elif expr.has_key('union'):
             add_union(expr)
-            add_enum('%sKind' % expr['union'])
+            enum_define = discriminator_find_enum_define(expr)
+            if not enum_define:
+                add_enum('%sKind' % expr['union'])
         elif expr.has_key('type'):
             add_struct(expr)
         exprs.append(expr)
