diff --git a/scripts/qapi/events.py b/scripts/qapi/events.py
index 599f3d1f56..9851653b9d 100644
--- a/scripts/qapi/events.py
+++ b/scripts/qapi/events.py
@@ -12,7 +12,7 @@ This work is licensed under the terms of the GNU GPL, version 2.
 See the COPYING file in the top-level directory.
 """
 
-from typing import List
+from typing import List, Optional
 
 from .common import c_enum_const, c_name, mcgen
 from .gen import QAPISchemaModularCVisitor, build_params, ifcontext
@@ -27,7 +27,7 @@ from .types import gen_enum, gen_enum_lookup
 
 
 def build_event_send_proto(name: str,
-                           arg_type: QAPISchemaObjectType,
+                           arg_type: Optional[QAPISchemaObjectType],
                            boxed: bool) -> str:
     return 'void qapi_event_send_%(c_name)s(%(param)s)' % {
         'c_name': c_name(name.lower()),
@@ -35,7 +35,7 @@ def build_event_send_proto(name: str,
 
 
 def gen_event_send_decl(name: str,
-                        arg_type: QAPISchemaObjectType,
+                        arg_type: Optional[QAPISchemaObjectType],
                         boxed: bool) -> str:
     return mcgen('''
 
@@ -78,7 +78,7 @@ def gen_param_var(typ: QAPISchemaObjectType) -> str:
 
 
 def gen_event_send(name: str,
-                   arg_type: QAPISchemaObjectType,
+                   arg_type: Optional[QAPISchemaObjectType],
                    boxed: bool,
                    event_enum_name: str,
                    event_emit: str) -> str:
@@ -99,6 +99,7 @@ def gen_event_send(name: str,
                 proto=build_event_send_proto(name, arg_type, boxed))
 
     if have_args:
+        assert arg_type is not None
         ret += mcgen('''
     QObject *obj;
     Visitor *v;
@@ -114,6 +115,7 @@ def gen_event_send(name: str,
                  name=name)
 
     if have_args:
+        assert arg_type is not None
         ret += mcgen('''
     v = qobject_output_visitor_new(&obj);
 ''')
@@ -214,7 +216,7 @@ void %(event_emit)s(%(event_enum)s event, QDict *qdict);
                     info: QAPISourceInfo,
                     ifcond: List[str],
                     features: List[QAPISchemaFeature],
-                    arg_type: QAPISchemaObjectType,
+                    arg_type: Optional[QAPISchemaObjectType],
                     boxed: bool) -> None:
         with ifcontext(ifcond, self._genh, self._genc):
             self._genh.add(gen_event_send_decl(name, arg_type, boxed))