diff --git a/scripts/qapi/gen.py b/scripts/qapi/gen.py
index 75471c4cc2..eec941074b 100644
--- a/scripts/qapi/gen.py
+++ b/scripts/qapi/gen.py
@@ -17,7 +17,13 @@
 import errno
 import os
 import re
-from typing import Optional
+from typing import (
+    Dict,
+    Iterator,
+    List,
+    Optional,
+    Tuple,
+)
 
 from .common import (
     c_fname,
@@ -29,31 +35,31 @@
     mcgen,
 )
 from .schema import QAPISchemaObjectType, QAPISchemaVisitor
+from .source import QAPISourceInfo
 
 
 class QAPIGen:
-
-    def __init__(self, fname):
+    def __init__(self, fname: Optional[str]):
         self.fname = fname
         self._preamble = ''
         self._body = ''
 
-    def preamble_add(self, text):
+    def preamble_add(self, text: str) -> None:
         self._preamble += text
 
-    def add(self, text):
+    def add(self, text: str) -> None:
         self._body += text
 
-    def get_content(self):
+    def get_content(self) -> str:
         return self._top() + self._preamble + self._body + self._bottom()
 
-    def _top(self):
+    def _top(self) -> str:
         return ''
 
-    def _bottom(self):
+    def _bottom(self) -> str:
         return ''
 
-    def write(self, output_dir):
+    def write(self, output_dir: str) -> None:
         # Include paths starting with ../ are used to reuse modules of the main
         # schema in specialised schemas. Don't overwrite the files that are
         # already generated for the main schema.
@@ -78,7 +84,7 @@ def write(self, output_dir):
         f.close()
 
 
-def _wrap_ifcond(ifcond, before, after):
+def _wrap_ifcond(ifcond: List[str], before: str, after: str) -> str:
     if before == after:
         return after   # suppress empty #if ... #endif
 
@@ -118,40 +124,38 @@ def build_params(arg_type: Optional[QAPISchemaObjectType],
 
 
 class QAPIGenCCode(QAPIGen):
-
-    def __init__(self, fname):
+    def __init__(self, fname: Optional[str]):
         super().__init__(fname)
-        self._start_if = None
+        self._start_if: Optional[Tuple[List[str], str, str]] = None
 
-    def start_if(self, ifcond):
+    def start_if(self, ifcond: List[str]) -> None:
         assert self._start_if is None
         self._start_if = (ifcond, self._body, self._preamble)
 
-    def end_if(self):
+    def end_if(self) -> None:
         assert self._start_if
         self._wrap_ifcond()
         self._start_if = None
 
-    def _wrap_ifcond(self):
+    def _wrap_ifcond(self) -> None:
         self._body = _wrap_ifcond(self._start_if[0],
                                   self._start_if[1], self._body)
         self._preamble = _wrap_ifcond(self._start_if[0],
                                       self._start_if[2], self._preamble)
 
-    def get_content(self):
+    def get_content(self) -> str:
         assert self._start_if is None
         return super().get_content()
 
 
 class QAPIGenC(QAPIGenCCode):
-
-    def __init__(self, fname, blurb, pydoc):
+    def __init__(self, fname: str, blurb: str, pydoc: str):
         super().__init__(fname)
         self._blurb = blurb
         self._copyright = '\n * '.join(re.findall(r'^Copyright .*', pydoc,
                                                   re.MULTILINE))
 
-    def _top(self):
+    def _top(self) -> str:
         return mcgen('''
 /* AUTOMATICALLY GENERATED, DO NOT MODIFY */
 
@@ -167,7 +171,7 @@ def _top(self):
 ''',
                      blurb=self._blurb, copyright=self._copyright)
 
-    def _bottom(self):
+    def _bottom(self) -> str:
         return mcgen('''
 
 /* Dummy declaration to prevent empty .o file */
@@ -177,16 +181,15 @@ def _bottom(self):
 
 
 class QAPIGenH(QAPIGenC):
-
-    def _top(self):
+    def _top(self) -> str:
         return super()._top() + guardstart(self.fname)
 
-    def _bottom(self):
+    def _bottom(self) -> str:
         return guardend(self.fname)
 
 
 @contextmanager
-def ifcontext(ifcond, *args):
+def ifcontext(ifcond: List[str], *args: QAPIGenCCode) -> Iterator[None]:
     """
     A 'with' statement context manager to wrap with start_if()/end_if()
 
@@ -214,15 +217,17 @@ def ifcontext(ifcond, *args):
 
 
 class QAPIGenDoc(QAPIGen):
-
-    def _top(self):
+    def _top(self) -> str:
         return (super()._top()
                 + '@c AUTOMATICALLY GENERATED, DO NOT MODIFY\n\n')
 
 
 class QAPISchemaMonolithicCVisitor(QAPISchemaVisitor):
-
-    def __init__(self, prefix, what, blurb, pydoc):
+    def __init__(self,
+                 prefix: str,
+                 what: str,
+                 blurb: str,
+                 pydoc: str):
         self._prefix = prefix
         self._what = what
         self._genc = QAPIGenC(self._prefix + self._what + '.c',
@@ -230,38 +235,42 @@ def __init__(self, prefix, what, blurb, pydoc):
         self._genh = QAPIGenH(self._prefix + self._what + '.h',
                               blurb, pydoc)
 
-    def write(self, output_dir):
+    def write(self, output_dir: str) -> None:
         self._genc.write(output_dir)
         self._genh.write(output_dir)
 
 
 class QAPISchemaModularCVisitor(QAPISchemaVisitor):
-
-    def __init__(self, prefix, what, user_blurb, builtin_blurb, pydoc):
+    def __init__(self,
+                 prefix: str,
+                 what: str,
+                 user_blurb: str,
+                 builtin_blurb: Optional[str],
+                 pydoc: str):
         self._prefix = prefix
         self._what = what
         self._user_blurb = user_blurb
         self._builtin_blurb = builtin_blurb
         self._pydoc = pydoc
-        self._genc = None
-        self._genh = None
-        self._module = {}
-        self._main_module = None
+        self._genc: Optional[QAPIGenC] = None
+        self._genh: Optional[QAPIGenH] = None
+        self._module: Dict[Optional[str], Tuple[QAPIGenC, QAPIGenH]] = {}
+        self._main_module: Optional[str] = None
 
     @staticmethod
-    def _is_user_module(name):
+    def _is_user_module(name: Optional[str]) -> bool:
         return bool(name and not name.startswith('./'))
 
     @staticmethod
-    def _is_builtin_module(name):
+    def _is_builtin_module(name: Optional[str]) -> bool:
         return not name
 
-    def _module_dirname(self, what, name):
+    def _module_dirname(self, what: str, name: Optional[str]) -> str:
         if self._is_user_module(name):
             return os.path.dirname(name)
         return ''
 
-    def _module_basename(self, what, name):
+    def _module_basename(self, what: str, name: Optional[str]) -> str:
         ret = '' if self._is_builtin_module(name) else self._prefix
         if self._is_user_module(name):
             basename = os.path.basename(name)
@@ -273,27 +282,27 @@ def _module_basename(self, what, name):
             ret += re.sub(r'-', '-' + name + '-', what)
         return ret
 
-    def _module_filename(self, what, name):
+    def _module_filename(self, what: str, name: Optional[str]) -> str:
         return os.path.join(self._module_dirname(what, name),
                             self._module_basename(what, name))
 
-    def _add_module(self, name, blurb):
+    def _add_module(self, name: Optional[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)
         self._module[name] = (genc, genh)
         self._genc, self._genh = self._module[name]
 
-    def _add_user_module(self, name, blurb):
+    def _add_user_module(self, name: str, blurb: str) -> None:
         assert self._is_user_module(name)
         if self._main_module is None:
             self._main_module = name
         self._add_module(name, blurb)
 
-    def _add_system_module(self, name, blurb):
+    def _add_system_module(self, name: Optional[str], blurb: str) -> None:
         self._add_module(name and './' + name, blurb)
 
-    def write(self, output_dir, opt_builtins=False):
+    def write(self, output_dir: str, opt_builtins: bool = False) -> None:
         for name in self._module:
             if self._is_builtin_module(name) and not opt_builtins:
                 continue
@@ -301,13 +310,13 @@ def write(self, output_dir, opt_builtins=False):
             genc.write(output_dir)
             genh.write(output_dir)
 
-    def _begin_system_module(self, name):
+    def _begin_system_module(self, name: None) -> None:
         pass
 
-    def _begin_user_module(self, name):
+    def _begin_user_module(self, name: str) -> None:
         pass
 
-    def visit_module(self, name):
+    def visit_module(self, name: Optional[str]) -> None:
         if name is None:
             if self._builtin_blurb:
                 self._add_system_module(None, self._builtin_blurb)
@@ -321,7 +330,7 @@ def visit_module(self, name):
             self._add_user_module(name, self._user_blurb)
             self._begin_user_module(name)
 
-    def visit_include(self, name, info):
+    def visit_include(self, name: str, info: QAPISourceInfo) -> None:
         relname = os.path.relpath(self._module_filename(self._what, name),
                                   os.path.dirname(self._genh.fname))
         self._genh.preamble_add(mcgen('''
