diff --git a/docs/qapi-code-gen.txt b/docs/qapi-code-gen.txt
index e0b2ef1..c648f76 100644
--- a/docs/qapi-code-gen.txt
+++ b/docs/qapi-code-gen.txt
@@ -575,9 +575,9 @@ names an object type without members.
 Example: the SchemaInfo for command query-qmp-schema
 
     { "name": "query-qmp-schema", "meta-type": "command",
-      "arg-type": ":empty", "ret-type": "SchemaInfoList" }
+      "arg-type": "q_empty", "ret-type": "SchemaInfoList" }
 
-    Type ":empty" is an object type without members, and type
+    Type "q_empty" is an automatic object type without members, and type
     "SchemaInfoList" is the array of SchemaInfo type.
 
 The SchemaInfo for an event has meta-type "event", and variant member
@@ -594,9 +594,9 @@ QAPI schema implicitly defines an object type.
 Example: the SchemaInfo for EVENT_C from section Events
 
     { "name": "EVENT_C", "meta-type": "event",
-      "arg-type": ":obj-EVENT_C-arg" }
+      "arg-type": "q_obj-EVENT_C-arg" }
 
-    Type ":obj-EVENT_C-arg" is an implicitly defined object type with
+    Type "q_obj-EVENT_C-arg" is an implicitly defined object type with
     the two members from the event's definition.
 
 The SchemaInfo for struct and union types has meta-type "object".
@@ -660,11 +660,11 @@ Union types
           { "name": "type", "type": "BlockdevOptionsKind" } ],
       "tag": "type",
       "variants": [
-          { "case": "file", "type": ":obj-FileOptions-wrapper" },
-          { "case": "qcow2", "type": ":obj-Qcow2Options-wrapper" } ] }
+          { "case": "file", "type": "q_obj-FileOptions-wrapper" },
+          { "case": "qcow2", "type": "q_obj-Qcow2Options-wrapper" } ] }
 
     Enumeration type "BlockdevOptionsKind" and the object types
-    ":obj-FileOptions-wrapper", ":obj-Qcow2Options-wrapper" are
+    "q_obj-FileOptions-wrapper", "q_obj-Qcow2Options-wrapper" are
     implicitly defined.
 
 The SchemaInfo for an alternate type has meta-type "alternate", and
diff --git a/scripts/qapi.py b/scripts/qapi.py
index b7fbdae..f6701f5 100644
--- a/scripts/qapi.py
+++ b/scripts/qapi.py
@@ -391,7 +391,8 @@ def check_name(expr_info, source, name, allow_optional=False,
     # code always prefixes it with the enum name
     if enum_member and membername[0].isdigit():
         membername = 'D' + membername
-    # Reserve the entire 'q_' namespace for c_name()
+    # Reserve the entire 'q_' namespace for c_name(), and for 'q_empty'
+    # and 'q_obj_*' implicit type names.
     if not valid_name.match(membername) or \
        c_name(membername, False).startswith('q_'):
         raise QAPIExprError(expr_info,
@@ -994,8 +995,9 @@ class QAPISchemaObjectType(QAPISchemaType):
             m.check_clash(info, seen)
 
     def is_implicit(self):
-        # See QAPISchema._make_implicit_object_type()
-        return self.name[0] == ':'
+        # See QAPISchema._make_implicit_object_type(), as well as
+        # _def_predefineds()
+        return self.name.startswith('q_')
 
     def c_name(self):
         assert not self.is_implicit()
@@ -1044,10 +1046,10 @@ class QAPISchemaMember(object):
 
     def _pretty_owner(self):
         owner = self.owner
-        if owner.startswith(':obj-'):
+        if owner.startswith('q_obj_'):
             # See QAPISchema._make_implicit_object_type() - reverse the
             # mapping there to create a nice human-readable description
-            owner = owner[5:]
+            owner = owner[6:]
             if owner.endswith('-arg'):
                 return '(parameter of %s)' % owner[:-4]
             else:
@@ -1266,8 +1268,8 @@ class QAPISchema(object):
                   ('bool',   'boolean', 'bool',     'false'),
                   ('any',    'value',   'QObject' + pointer_suffix, 'NULL')]:
             self._def_builtin_type(*t)
-        self.the_empty_object_type = QAPISchemaObjectType(':empty', None, None,
-                                                          [], None)
+        self.the_empty_object_type = QAPISchemaObjectType('q_empty', None,
+                                                          None, [], None)
         self._def_entity(self.the_empty_object_type)
         qtype_values = self._make_enum_members(['none', 'qnull', 'qint',
                                                 'qstring', 'qdict', 'qlist',
@@ -1295,7 +1297,7 @@ class QAPISchema(object):
         if not members:
             return None
         # See also QAPISchemaObjectTypeMember._pretty_owner()
-        name = ':obj-%s-%s' % (name, role)
+        name = 'q_obj_%s-%s' % (name, role)
         if not self.lookup_entity(name, QAPISchemaObjectType):
             self._def_entity(QAPISchemaObjectType(name, info, None,
                                                   members, None))
diff --git a/tests/qapi-schema/comments.out b/tests/qapi-schema/comments.out
index 97be601..5d7c13c 100644
--- a/tests/qapi-schema/comments.out
+++ b/tests/qapi-schema/comments.out
@@ -1,4 +1,4 @@
-object :empty
 enum QType ['none', 'qnull', 'qint', 'qstring', 'qdict', 'qlist', 'qfloat', 'qbool']
     prefix QTYPE
 enum Status ['good', 'bad', 'ugly']
+object q_empty
diff --git a/tests/qapi-schema/empty.out b/tests/qapi-schema/empty.out
index 6522940..8a5b034 100644
--- a/tests/qapi-schema/empty.out
+++ b/tests/qapi-schema/empty.out
@@ -1,3 +1,3 @@
-object :empty
 enum QType ['none', 'qnull', 'qint', 'qstring', 'qdict', 'qlist', 'qfloat', 'qbool']
     prefix QTYPE
+object q_empty
diff --git a/tests/qapi-schema/event-case.out b/tests/qapi-schema/event-case.out
index 6350d64..b6b4134 100644
--- a/tests/qapi-schema/event-case.out
+++ b/tests/qapi-schema/event-case.out
@@ -1,4 +1,4 @@
-object :empty
 enum QType ['none', 'qnull', 'qint', 'qstring', 'qdict', 'qlist', 'qfloat', 'qbool']
     prefix QTYPE
 event oops None
+object q_empty
diff --git a/tests/qapi-schema/ident-with-escape.out b/tests/qapi-schema/ident-with-escape.out
index 453e0b2..382ce2f 100644
--- a/tests/qapi-schema/ident-with-escape.out
+++ b/tests/qapi-schema/ident-with-escape.out
@@ -1,7 +1,7 @@
-object :empty
-object :obj-fooA-arg
-    member bar1: str optional=False
 enum QType ['none', 'qnull', 'qint', 'qstring', 'qdict', 'qlist', 'qfloat', 'qbool']
     prefix QTYPE
-command fooA :obj-fooA-arg -> None
+command fooA q_obj_fooA-arg -> None
    gen=True success_response=True
+object q_empty
+object q_obj_fooA-arg
+    member bar1: str optional=False
diff --git a/tests/qapi-schema/include-relpath.out b/tests/qapi-schema/include-relpath.out
index 97be601..5d7c13c 100644
--- a/tests/qapi-schema/include-relpath.out
+++ b/tests/qapi-schema/include-relpath.out
@@ -1,4 +1,4 @@
-object :empty
 enum QType ['none', 'qnull', 'qint', 'qstring', 'qdict', 'qlist', 'qfloat', 'qbool']
     prefix QTYPE
 enum Status ['good', 'bad', 'ugly']
+object q_empty
diff --git a/tests/qapi-schema/include-repetition.out b/tests/qapi-schema/include-repetition.out
index 97be601..5d7c13c 100644
--- a/tests/qapi-schema/include-repetition.out
+++ b/tests/qapi-schema/include-repetition.out
@@ -1,4 +1,4 @@
-object :empty
 enum QType ['none', 'qnull', 'qint', 'qstring', 'qdict', 'qlist', 'qfloat', 'qbool']
     prefix QTYPE
 enum Status ['good', 'bad', 'ugly']
+object q_empty
diff --git a/tests/qapi-schema/include-simple.out b/tests/qapi-schema/include-simple.out
index 97be601..5d7c13c 100644
--- a/tests/qapi-schema/include-simple.out
+++ b/tests/qapi-schema/include-simple.out
@@ -1,4 +1,4 @@
-object :empty
 enum QType ['none', 'qnull', 'qint', 'qstring', 'qdict', 'qlist', 'qfloat', 'qbool']
     prefix QTYPE
 enum Status ['good', 'bad', 'ugly']
+object q_empty
diff --git a/tests/qapi-schema/indented-expr.out b/tests/qapi-schema/indented-expr.out
index ce37ff5..ae3293a 100644
--- a/tests/qapi-schema/indented-expr.out
+++ b/tests/qapi-schema/indented-expr.out
@@ -1,7 +1,7 @@
-object :empty
 enum QType ['none', 'qnull', 'qint', 'qstring', 'qdict', 'qlist', 'qfloat', 'qbool']
     prefix QTYPE
 command eins None -> None
    gen=True success_response=True
+object q_empty
 command zwei None -> None
    gen=True success_response=True
diff --git a/tests/qapi-schema/qapi-schema-test.out b/tests/qapi-schema/qapi-schema-test.out
index f531961..d49fe1d 100644
--- a/tests/qapi-schema/qapi-schema-test.out
+++ b/tests/qapi-schema/qapi-schema-test.out
@@ -1,58 +1,3 @@
-object :empty
-object :obj-EVENT_C-arg
-    member a: int optional=True
-    member b: UserDefOne optional=True
-    member c: str optional=False
-object :obj-EVENT_D-arg
-    member a: EventStructOne optional=False
-    member b: str optional=False
-    member c: str optional=True
-    member enum3: EnumOne optional=True
-object :obj-__org.qemu_x-command-arg
-    member a: __org.qemu_x-EnumList optional=False
-    member b: __org.qemu_x-StructList optional=False
-    member c: __org.qemu_x-Union2 optional=False
-    member d: __org.qemu_x-Alt optional=False
-object :obj-anyList-wrapper
-    member data: anyList optional=False
-object :obj-boolList-wrapper
-    member data: boolList optional=False
-object :obj-guest-get-time-arg
-    member a: int optional=False
-    member b: int optional=True
-object :obj-guest-sync-arg
-    member arg: any optional=False
-object :obj-int16List-wrapper
-    member data: int16List optional=False
-object :obj-int32List-wrapper
-    member data: int32List optional=False
-object :obj-int64List-wrapper
-    member data: int64List optional=False
-object :obj-int8List-wrapper
-    member data: int8List optional=False
-object :obj-intList-wrapper
-    member data: intList optional=False
-object :obj-numberList-wrapper
-    member data: numberList optional=False
-object :obj-sizeList-wrapper
-    member data: sizeList optional=False
-object :obj-str-wrapper
-    member data: str optional=False
-object :obj-strList-wrapper
-    member data: strList optional=False
-object :obj-uint16List-wrapper
-    member data: uint16List optional=False
-object :obj-uint32List-wrapper
-    member data: uint32List optional=False
-object :obj-uint64List-wrapper
-    member data: uint64List optional=False
-object :obj-uint8List-wrapper
-    member data: uint8List optional=False
-object :obj-user_def_cmd1-arg
-    member ud1a: UserDefOne optional=False
-object :obj-user_def_cmd2-arg
-    member ud1a: UserDefOne optional=False
-    member ud1b: UserDefOne optional=True
 alternate AltIntNum
     case i: int
     case n: number
@@ -73,8 +18,8 @@ alternate AltStrNum
     case n: number
 event EVENT_A None
 event EVENT_B None
-event EVENT_C :obj-EVENT_C-arg
-event EVENT_D :obj-EVENT_D-arg
+event EVENT_C q_obj_EVENT_C-arg
+event EVENT_D q_obj_EVENT_D-arg
 object Empty1
 object Empty2
     base Empty1
@@ -127,20 +72,20 @@ object UserDefFlatUnion2
     case value2: UserDefB
 object UserDefNativeListUnion
     member type: UserDefNativeListUnionKind optional=False
-    case integer: :obj-intList-wrapper
-    case s8: :obj-int8List-wrapper
-    case s16: :obj-int16List-wrapper
-    case s32: :obj-int32List-wrapper
-    case s64: :obj-int64List-wrapper
-    case u8: :obj-uint8List-wrapper
-    case u16: :obj-uint16List-wrapper
-    case u32: :obj-uint32List-wrapper
-    case u64: :obj-uint64List-wrapper
-    case number: :obj-numberList-wrapper
-    case boolean: :obj-boolList-wrapper
-    case string: :obj-strList-wrapper
-    case sizes: :obj-sizeList-wrapper
-    case any: :obj-anyList-wrapper
+    case integer: q_obj_intList-wrapper
+    case s8: q_obj_int8List-wrapper
+    case s16: q_obj_int16List-wrapper
+    case s32: q_obj_int32List-wrapper
+    case s64: q_obj_int64List-wrapper
+    case u8: q_obj_uint8List-wrapper
+    case u16: q_obj_uint16List-wrapper
+    case u32: q_obj_uint32List-wrapper
+    case u64: q_obj_uint64List-wrapper
+    case number: q_obj_numberList-wrapper
+    case boolean: q_obj_boolList-wrapper
+    case string: q_obj_strList-wrapper
+    case sizes: q_obj_sizeList-wrapper
+    case any: q_obj_anyList-wrapper
 enum UserDefNativeListUnionKind ['integer', 's8', 's16', 's32', 's64', 'u8', 'u16', 'u32', 'u64', 'number', 'boolean', 'string', 'sizes', 'any']
 object UserDefOne
     base UserDefZero
@@ -189,23 +134,78 @@ object __org.qemu_x-Struct2
     member array: __org.qemu_x-Union1List optional=False
 object __org.qemu_x-Union1
     member type: __org.qemu_x-Union1Kind optional=False
-    case __org.qemu_x-branch: :obj-str-wrapper
+    case __org.qemu_x-branch: q_obj_str-wrapper
 enum __org.qemu_x-Union1Kind ['__org.qemu_x-branch']
 object __org.qemu_x-Union2
     base __org.qemu_x-Base
     tag __org.qemu_x-member1
     case __org.qemu_x-value: __org.qemu_x-Struct2
-command __org.qemu_x-command :obj-__org.qemu_x-command-arg -> __org.qemu_x-Union1
+command __org.qemu_x-command q_obj___org.qemu_x-command-arg -> __org.qemu_x-Union1
    gen=True success_response=True
-command guest-get-time :obj-guest-get-time-arg -> int
+command guest-get-time q_obj_guest-get-time-arg -> int
    gen=True success_response=True
-command guest-sync :obj-guest-sync-arg -> any
+command guest-sync q_obj_guest-sync-arg -> any
    gen=True success_response=True
+object q_empty
+object q_obj_EVENT_C-arg
+    member a: int optional=True
+    member b: UserDefOne optional=True
+    member c: str optional=False
+object q_obj_EVENT_D-arg
+    member a: EventStructOne optional=False
+    member b: str optional=False
+    member c: str optional=True
+    member enum3: EnumOne optional=True
+object q_obj___org.qemu_x-command-arg
+    member a: __org.qemu_x-EnumList optional=False
+    member b: __org.qemu_x-StructList optional=False
+    member c: __org.qemu_x-Union2 optional=False
+    member d: __org.qemu_x-Alt optional=False
+object q_obj_anyList-wrapper
+    member data: anyList optional=False
+object q_obj_boolList-wrapper
+    member data: boolList optional=False
+object q_obj_guest-get-time-arg
+    member a: int optional=False
+    member b: int optional=True
+object q_obj_guest-sync-arg
+    member arg: any optional=False
+object q_obj_int16List-wrapper
+    member data: int16List optional=False
+object q_obj_int32List-wrapper
+    member data: int32List optional=False
+object q_obj_int64List-wrapper
+    member data: int64List optional=False
+object q_obj_int8List-wrapper
+    member data: int8List optional=False
+object q_obj_intList-wrapper
+    member data: intList optional=False
+object q_obj_numberList-wrapper
+    member data: numberList optional=False
+object q_obj_sizeList-wrapper
+    member data: sizeList optional=False
+object q_obj_str-wrapper
+    member data: str optional=False
+object q_obj_strList-wrapper
+    member data: strList optional=False
+object q_obj_uint16List-wrapper
+    member data: uint16List optional=False
+object q_obj_uint32List-wrapper
+    member data: uint32List optional=False
+object q_obj_uint64List-wrapper
+    member data: uint64List optional=False
+object q_obj_uint8List-wrapper
+    member data: uint8List optional=False
+object q_obj_user_def_cmd1-arg
+    member ud1a: UserDefOne optional=False
+object q_obj_user_def_cmd2-arg
+    member ud1a: UserDefOne optional=False
+    member ud1b: UserDefOne optional=True
 command user_def_cmd None -> None
    gen=True success_response=True
 command user_def_cmd0 Empty2 -> Empty2
    gen=True success_response=True
-command user_def_cmd1 :obj-user_def_cmd1-arg -> None
+command user_def_cmd1 q_obj_user_def_cmd1-arg -> None
    gen=True success_response=True
-command user_def_cmd2 :obj-user_def_cmd2-arg -> UserDefTwo
+command user_def_cmd2 q_obj_user_def_cmd2-arg -> UserDefTwo
    gen=True success_response=True
