diff --git a/scripts/qapi/gen.py b/scripts/qapi/gen.py
index da9d4d2d37..9352d79c3a 100644
--- a/scripts/qapi/gen.py
+++ b/scripts/qapi/gen.py
@@ -246,16 +246,16 @@ def __init__(self,
         self._pydoc = pydoc
         self._genc: Optional[QAPIGenC] = None
         self._genh: Optional[QAPIGenH] = None
-        self._module: Dict[Optional[str], Tuple[QAPIGenC, QAPIGenH]] = {}
+        self._module: Dict[str, Tuple[QAPIGenC, QAPIGenH]] = {}
         self._main_module: Optional[str] = None
 
     @staticmethod
-    def _module_dirname(name: Optional[str]) -> str:
+    def _module_dirname(name: str) -> str:
         if QAPISchemaModule.is_user_module(name):
             return os.path.dirname(name)
         return ''
 
-    def _module_basename(self, what: str, name: Optional[str]) -> str:
+    def _module_basename(self, what: str, name: str) -> str:
         ret = '' if QAPISchemaModule.is_builtin_module(name) else self._prefix
         if QAPISchemaModule.is_user_module(name):
             basename = os.path.basename(name)
@@ -263,15 +263,15 @@ def _module_basename(self, what: str, name: Optional[str]) -> str:
             if name != self._main_module:
                 ret += '-' + os.path.splitext(basename)[0]
         else:
-            name = name[2:] if name else 'builtin'
-            ret += re.sub(r'-', '-' + name + '-', what)
+            assert QAPISchemaModule.is_system_module(name)
+            ret += re.sub(r'-', '-' + name[2:] + '-', what)
         return ret
 
-    def _module_filename(self, what: str, name: Optional[str]) -> str:
+    def _module_filename(self, what: str, name: str) -> str:
         return os.path.join(self._module_dirname(name),
                             self._module_basename(what, name))
 
-    def _add_module(self, name: Optional[str], blurb: str) -> None:
+    def _add_module(self, name: str, blurb: str) -> None:
         basename = self._module_filename(self._what, name)
         genc = QAPIGenC(basename + '.c', blurb, self._pydoc)
         genh = QAPIGenH(basename + '.h', blurb, self._pydoc)
@@ -284,7 +284,7 @@ def _add_user_module(self, name: str, blurb: str) -> None:
             self._main_module = name
         self._add_module(name, blurb)
 
-    def _add_system_module(self, name: Optional[str], blurb: str) -> None:
+    def _add_system_module(self, name: str, blurb: str) -> None:
         assert QAPISchemaModule.is_system_module(name)
         self._add_module(name, blurb)
 
@@ -302,7 +302,7 @@ def _begin_builtin_module(self) -> None:
     def _begin_user_module(self, name: str) -> None:
         pass
 
-    def visit_module(self, name: Optional[str]) -> None:
+    def visit_module(self, name: str) -> None:
         if QAPISchemaModule.is_builtin_module(name):
             if self._builtin_blurb:
                 self._add_system_module(name, self._builtin_blurb)
diff --git a/scripts/qapi/schema.py b/scripts/qapi/schema.py
index e80d9320ed..14cf9da784 100644
--- a/scripts/qapi/schema.py
+++ b/scripts/qapi/schema.py
@@ -68,7 +68,8 @@ def check_doc(self):
 
     def _set_module(self, schema, info):
         assert self._checked
-        self._module = schema.module_by_fname(info and info.fname)
+        fname = info.fname if info else './builtin'
+        self._module = schema.module_by_fname(fname)
         self._module.add_entity(self)
 
     def set_module(self, schema):
@@ -142,16 +143,16 @@ def __init__(self, name):
         self._entity_list = []
 
     @staticmethod
-    def is_system_module(name: Optional[str]) -> bool:
+    def is_system_module(name: str) -> bool:
         """
         System modules are internally defined modules.
 
         Their names start with the "./" prefix.
         """
-        return name is None or name.startswith('./')
+        return name.startswith('./')
 
     @classmethod
-    def is_user_module(cls, name: Optional[str]) -> bool:
+    def is_user_module(cls, name: str) -> bool:
         """
         User modules are those defined by the user in qapi JSON files.
 
@@ -160,13 +161,13 @@ def is_user_module(cls, name: Optional[str]) -> bool:
         return not cls.is_system_module(name)
 
     @staticmethod
-    def is_builtin_module(name: Optional[str]) -> bool:
+    def is_builtin_module(name: str) -> bool:
         """
         The built-in module is a single System module for the built-in types.
 
-        It is presently always the value 'None'.
+        It is always "./builtin".
         """
-        return name is None
+        return name == './builtin'
 
     def add_entity(self, ent):
         self._entity_list.append(ent)
@@ -852,7 +853,7 @@ def __init__(self, fname):
         self._entity_dict = {}
         self._module_dict = OrderedDict()
         self._schema_dir = os.path.dirname(fname)
-        self._make_module(None)  # built-ins
+        self._make_module('./builtin')
         self._make_module(fname)
         self._predefining = True
         self._def_predefineds()
@@ -897,7 +898,7 @@ def resolve_type(self, name, info, what):
                 info, "%s uses unknown type '%s'" % (what, name))
         return typ
 
-    def _module_name(self, fname):
+    def _module_name(self, fname: str) -> str:
         if QAPISchemaModule.is_system_module(fname):
             return fname
         return os.path.relpath(fname, self._schema_dir)
@@ -910,7 +911,6 @@ def _make_module(self, fname):
 
     def module_by_fname(self, fname):
         name = self._module_name(fname)
-        assert name in self._module_dict
         return self._module_dict[name]
 
     def _def_include(self, expr, info, doc):
diff --git a/tests/qapi-schema/comments.out b/tests/qapi-schema/comments.out
index 273f0f54e1..ce4f6a4f0f 100644
--- a/tests/qapi-schema/comments.out
+++ b/tests/qapi-schema/comments.out
@@ -1,4 +1,4 @@
-module None
+module ./builtin
 object q_empty
 enum QType
     prefix QTYPE
diff --git a/tests/qapi-schema/doc-good.out b/tests/qapi-schema/doc-good.out
index 419284dae2..715b0bbc1a 100644
--- a/tests/qapi-schema/doc-good.out
+++ b/tests/qapi-schema/doc-good.out
@@ -1,4 +1,4 @@
-module None
+module ./builtin
 object q_empty
 enum QType
     prefix QTYPE
diff --git a/tests/qapi-schema/empty.out b/tests/qapi-schema/empty.out
index 69666c39ad..3feb3f69d3 100644
--- a/tests/qapi-schema/empty.out
+++ b/tests/qapi-schema/empty.out
@@ -1,4 +1,4 @@
-module None
+module ./builtin
 object q_empty
 enum QType
     prefix QTYPE
diff --git a/tests/qapi-schema/event-case.out b/tests/qapi-schema/event-case.out
index 42ae519656..9ae44052ac 100644
--- a/tests/qapi-schema/event-case.out
+++ b/tests/qapi-schema/event-case.out
@@ -1,4 +1,4 @@
-module None
+module ./builtin
 object q_empty
 enum QType
     prefix QTYPE
diff --git a/tests/qapi-schema/include-repetition.out b/tests/qapi-schema/include-repetition.out
index 0b654ddebb..16dbd9b819 100644
--- a/tests/qapi-schema/include-repetition.out
+++ b/tests/qapi-schema/include-repetition.out
@@ -1,4 +1,4 @@
-module None
+module ./builtin
 object q_empty
 enum QType
     prefix QTYPE
diff --git a/tests/qapi-schema/include-simple.out b/tests/qapi-schema/include-simple.out
index 061f81e509..48e923bfbc 100644
--- a/tests/qapi-schema/include-simple.out
+++ b/tests/qapi-schema/include-simple.out
@@ -1,4 +1,4 @@
-module None
+module ./builtin
 object q_empty
 enum QType
     prefix QTYPE
diff --git a/tests/qapi-schema/indented-expr.out b/tests/qapi-schema/indented-expr.out
index 04356775cd..6a30ded3fa 100644
--- a/tests/qapi-schema/indented-expr.out
+++ b/tests/qapi-schema/indented-expr.out
@@ -1,4 +1,4 @@
-module None
+module ./builtin
 object q_empty
 enum QType
     prefix QTYPE
diff --git a/tests/qapi-schema/qapi-schema-test.out b/tests/qapi-schema/qapi-schema-test.out
index 8868ca0dca..3b1387d9f1 100644
--- a/tests/qapi-schema/qapi-schema-test.out
+++ b/tests/qapi-schema/qapi-schema-test.out
@@ -1,4 +1,4 @@
-module None
+module ./builtin
 object q_empty
 enum QType
     prefix QTYPE