diff --git a/msvc/unicorn/qapi-visit.h b/msvc/unicorn/qapi-visit.h
index f7bba48b..3d695733 100644
--- a/msvc/unicorn/qapi-visit.h
+++ b/msvc/unicorn/qapi-visit.h
@@ -17,6 +17,7 @@
 #define QAPI_VISIT_H
 
 #include "qapi/visitor.h"
+#include "qapi/qmp/qerror.h"
 #include "qapi-types.h"
 
 
diff --git a/qemu/include/qapi/visitor-impl.h b/qemu/include/qapi/visitor-impl.h
index 6a45e11e..16181ad2 100644
--- a/qemu/include/qapi/visitor-impl.h
+++ b/qemu/include/qapi/visitor-impl.h
@@ -32,7 +32,8 @@ struct Visitor
 
     void (*type_enum)(Visitor *v, int *obj, const char * const strings[],
                       const char *kind, const char *name, Error **errp);
-    void (*get_next_type)(Visitor *v, int *kind, const int *qobjects,
+    /* May be NULL; only needed for input visitors. */
+    void (*get_next_type)(Visitor *v, QType *type,
                           const char *name, Error **errp);
     /* Must be set. */
     void (*type_int64)(Visitor *v, int64_t *obj, const char *name,
diff --git a/qemu/include/qapi/visitor.h b/qemu/include/qapi/visitor.h
index 6ca0ef98..94019d7a 100644
--- a/qemu/include/qapi/visitor.h
+++ b/qemu/include/qapi/visitor.h
@@ -38,7 +38,12 @@ GenericList *visit_next_list(Visitor *v, GenericList **list);
 void visit_end_list(Visitor *v);
 void visit_optional(Visitor *v, bool *present, const char *name,
                     Error **errp);
-void visit_get_next_type(Visitor *v, int *obj, const int *qtypes,
+/**
+ * Determine the qtype of the item @name in the current object visit.
+ * For input visitors, set *@type to the correct qtype of a qapi
+ * alternate type; for other visitors, leave *@type unchanged.
+ */
+void visit_get_next_type(Visitor *v, QType *type,
                          const char *name, Error **errp);
 void visit_type_enum(Visitor *v, int *obj, const char * const strings[],
                      const char *kind, const char *name, Error **errp);
diff --git a/qemu/qapi/qapi-visit-core.c b/qemu/qapi/qapi-visit-core.c
index 7cc341d5..5d77b487 100644
--- a/qemu/qapi/qapi-visit-core.c
+++ b/qemu/qapi/qapi-visit-core.c
@@ -82,11 +82,11 @@ void visit_optional(Visitor *v, bool *present, const char *name,
     }
 }
 
-void visit_get_next_type(Visitor *v, int *obj, const int *qtypes,
+void visit_get_next_type(Visitor *v, QType *type,
                          const char *name, Error **errp)
 {
     if (v->get_next_type) {
-        v->get_next_type(v, obj, qtypes, name, errp);
+        v->get_next_type(v, type, name, errp);
     }
 }
 
diff --git a/qemu/qapi/qmp-input-visitor.c b/qemu/qapi/qmp-input-visitor.c
index 5b2cf452..d5886491 100644
--- a/qemu/qapi/qmp-input-visitor.c
+++ b/qemu/qapi/qmp-input-visitor.c
@@ -208,7 +208,7 @@ static void qmp_input_end_list(Visitor *v)
     qmp_input_pop(qiv, &error_abort);
 }
 
-static void qmp_input_get_next_type(Visitor *v, int *kind, const int *qobjects,
+static void qmp_input_get_next_type(Visitor *v, QType *type,
                                     const char *name, Error **errp)
 {
     QmpInputVisitor *qiv = to_qiv(v);
@@ -218,7 +218,7 @@ static void qmp_input_get_next_type(Visitor *v, int *kind, const int *qobjects,
         error_setg(errp, QERR_MISSING_PARAMETER, name ? name : "null");
         return;
     }
-    *kind = qobjects[qobject_type(qobj)];
+    *type = qobject_type(qobj);
 }
 
 static void qmp_input_type_int64(Visitor *v, int64_t *obj, const char *name,
diff --git a/qemu/scripts/qapi-visit.py b/qemu/scripts/qapi-visit.py
index 233c9fcb..5180e9ca 100644
--- a/qemu/scripts/qapi-visit.py
+++ b/qemu/scripts/qapi-visit.py
@@ -169,6 +169,7 @@ out:
 
 
 def gen_visit_enum(name):
+    # FIXME cast from enum *obj to int * invalidly assumes enum is int
     return mcgen('''
 
 void visit_type_%(c_name)s(Visitor *v, %(c_name)s *obj, const char *name, Error **errp)
@@ -190,7 +191,7 @@ void visit_type_%(c_name)s(Visitor *v, %(c_name)s **obj, const char *name, Error
     if (err) {
         goto out;
     }
-    visit_get_next_type(v, (int*) &(*obj)->type, %(c_name)s_qtypes, name, &err);
+    visit_get_next_type(v, &(*obj)->type, name, &err);
     if (err) {
         goto out_obj;
     }
@@ -198,20 +199,22 @@ void visit_type_%(c_name)s(Visitor *v, %(c_name)s **obj, const char *name, Error
 ''',
                 c_name=c_name(name))
 
+    # FIXME: When 'number' but not 'int' is present in the alternate, we
+    # should allow QTYPE_INT to promote to QTYPE_FLOAT.
     for var in variants.variants:
         ret += mcgen('''
     case %(case)s:
         visit_type_%(c_type)s(v, &(*obj)->u.%(c_name)s, name, &err);
         break;
 ''',
-                     case=c_enum_const(variants.tag_member.type.name,
-                                       var.name),
+                     case=var.type.alternate_qtype(),
                      c_type=var.type.c_name(),
                      c_name=c_name(var.name))
 
     ret += mcgen('''
     default:
-        abort();
+        error_setg(&err, QERR_INVALID_PARAMETER_TYPE, name ? name : "null",
+                   "%(name)s");
     }
 out_obj:
     error_propagate(errp, err);
@@ -220,7 +223,8 @@ out_obj:
 out:
     error_propagate(errp, err);
 }
-''')
+''',
+                 name=name)
 
     return ret
 
@@ -436,6 +440,7 @@ fdef.write(mcgen('''
 
 fdecl.write(mcgen('''
 #include "qapi/visitor.h"
+#include "qapi/qmp/qerror.h"
 #include "%(prefix)sqapi-types.h"
 
 ''',
diff --git a/qemu/scripts/qapi.py b/qemu/scripts/qapi.py
index 9b3fdef0..be1e0852 100644
--- a/qemu/scripts/qapi.py
+++ b/qemu/scripts/qapi.py
@@ -637,8 +637,8 @@ def check_alternate(expr, expr_info):
     for (key, value) in members.items():
         check_name(expr_info, "Member of alternate '%s'" % name, key)
 
-        # Check for conflicts in the generated enum
-        c_key = camel_to_upper(key)
+        # Check for conflicts in the branch names
+        c_key = c_name(key)
         if c_key in values:
             raise QAPIExprError(expr_info,
                                 "Alternate '%s' member '%s' clashes with '%s'"
@@ -1095,8 +1095,11 @@ class QAPISchemaObjectTypeVariants(object):
         assert isinstance(self.tag_member.type, QAPISchemaEnumType)
         for v in self.variants:
             v.check(schema)
-            assert v.name in self.tag_member.type.values
-            if isinstance(v.type, QAPISchemaObjectType):
+            # Union names must match enum values; alternate names are
+            # checked separately. Use 'seen' to tell the two apart.
+            if seen:
+                assert v.name in self.tag_member.type.values
+                assert isinstance(v.type, QAPISchemaObjectType)
                 v.type.check(schema)
 
     def check_clash(self, schema, info, seen):
@@ -1136,6 +1139,11 @@ class QAPISchemaAlternateType(QAPISchemaType):
     def check(self, schema):
         self.variants.tag_member.check(schema)
         self.variants.check(schema, {})
+        # Alternate branch names have no relation to the tag enum values;
+        # so we have to check for potential name collisions ourselves.
+        seen = {}
+        for v in self.variants.variants:
+            v.check_clash(self.info, seen)
 
     def json_type(self):
         return 'value'
@@ -1343,7 +1351,7 @@ class QAPISchema(object):
         data = expr['data']
         variants = [self._make_variant(key, value)
                     for (key, value) in data.iteritems()]
-        tag_member = self._make_implicit_tag(name, info, variants)
+        tag_member = QAPISchemaObjectTypeMember('type', 'QType', False)
         self._def_entity(
             QAPISchemaAlternateType(name, info,
                                     QAPISchemaObjectTypeVariants(None,