diff --git a/python/qemu/machine.py b/python/qemu/machine.py
index 4e762fc..e599cb7 100644
--- a/python/qemu/machine.py
+++ b/python/qemu/machine.py
@@ -18,6 +18,7 @@
 #
 
 import errno
+from itertools import chain
 import logging
 import os
 import shutil
@@ -30,6 +31,8 @@
     Dict,
     List,
     Optional,
+    Sequence,
+    Tuple,
     Type,
 )
 
@@ -74,8 +77,12 @@
         # vm is guaranteed to be shut down here
     """
 
-    def __init__(self, binary, args=None, wrapper=None, name=None,
-                 test_dir="/var/tmp",
+    def __init__(self,
+                 binary: str,
+                 args: Sequence[str] = (),
+                 wrapper: Sequence[str] = (),
+                 name: Optional[str] = None,
+                 test_dir: str = "/var/tmp",
                  monitor_address: Optional[SocketAddrT] = None,
                  socket_scm_helper=None, sock_dir=None,
                  drain_console=False, console_log=None):
@@ -97,14 +104,7 @@
         # Direct user configuration
 
         self._binary = binary
-
-        if args is None:
-            args = []
-        # Copy mutable input: we will be modifying our copy
         self._args = list(args)
-
-        if wrapper is None:
-            wrapper = []
         self._wrapper = wrapper
 
         self._name = name or "qemu-%d" % os.getpid()
@@ -136,7 +136,7 @@
         self._iolog = None
         self._qmp_set = True   # Enable QMP monitor by default.
         self._qmp_connection: Optional[qmp.QEMUMonitorProtocol] = None
-        self._qemu_full_args = None
+        self._qemu_full_args: Tuple[str, ...] = ()
         self._temp_dir = None
         self._launched = False
         self._machine = None
@@ -368,7 +368,7 @@
             raise QEMUMachineError('VM already launched')
 
         self._iolog = None
-        self._qemu_full_args = None
+        self._qemu_full_args = ()
         try:
             self._launch()
             self._launched = True
@@ -388,8 +388,12 @@
         """
         devnull = open(os.path.devnull, 'rb')
         self._pre_launch()
-        self._qemu_full_args = (self._wrapper + [self._binary] +
-                                self._base_args + self._args)
+        self._qemu_full_args = tuple(
+            chain(self._wrapper,
+                  [self._binary],
+                  self._base_args,
+                  self._args)
+        )
         LOG.debug('VM launch command: %r', ' '.join(self._qemu_full_args))
         self._popen = subprocess.Popen(self._qemu_full_args,
                                        stdin=devnull,
diff --git a/python/qemu/qtest.py b/python/qemu/qtest.py
index 7fde256..675310d 100644
--- a/python/qemu/qtest.py
+++ b/python/qemu/qtest.py
@@ -19,7 +19,12 @@
 
 import os
 import socket
-from typing import List, Optional, TextIO
+from typing import (
+    List,
+    Optional,
+    Sequence,
+    TextIO,
+)
 
 from .machine import QEMUMachine
 
@@ -99,8 +104,13 @@
     A QEMU VM, with a qtest socket available.
     """
 
-    def __init__(self, binary, args=None, name=None, test_dir="/var/tmp",
-                 socket_scm_helper=None, sock_dir=None):
+    def __init__(self,
+                 binary: str,
+                 args: Sequence[str] = (),
+                 name: Optional[str] = None,
+                 test_dir: str = "/var/tmp",
+                 socket_scm_helper: Optional[str] = None,
+                 sock_dir: Optional[str] = None):
         if name is None:
             name = "qemu-%d" % os.getpid()
         if sock_dir is None:
@@ -114,8 +124,10 @@
     @property
     def _base_args(self) -> List[str]:
         args = super()._base_args
-        args.extend(['-qtest', 'unix:path=' + self._qtest_path,
-                     '-accel', 'qtest'])
+        args.extend([
+            '-qtest', f"unix:path={self._qtest_path}",
+            '-accel', 'qtest'
+        ])
         return args
 
     def _pre_launch(self):