diff --git a/.mypy.ini b/.mypy.ini
index c85c6d632..3373bdb28 100644
--- a/.mypy.ini
+++ b/.mypy.ini
@@ -60,6 +60,9 @@ strict_optional               = True
 [mypy-mesonbuild.mesondata]
 strict_optional               = True
 
+[mypy-mesonbuild.mesonmain]
+strict_optional               = True
+
 [mypy-mesonbuild.mlog]
 strict_optional               = True
 
diff --git a/mesonbuild/mesonmain.py b/mesonbuild/mesonmain.py
index ee2f5c8a8..a087ad277 100644
--- a/mesonbuild/mesonmain.py
+++ b/mesonbuild/mesonmain.py
@@ -57,7 +57,7 @@ def errorhandler(e: Exception, command: str) -> int:
         elif isinstance(e, OSError):
             mlog.exception(Exception("Unhandled python OSError. This is probably not a Meson bug, "
                            "but an issue with your build environment."))
-            return e.errno
+            return e.errno or 0
         else: # Exception
             msg = 'Unhandled python exception'
             if all(getattr(e, a, None) is not None for a in ['file', 'lineno', 'colno']):
@@ -126,7 +126,8 @@ class CommandLineParser:
                          help_msg=argparse.SUPPRESS)
 
     def add_command(self, name: str, add_arguments_func: T.Callable[[argparse.ArgumentParser], None],
-                    run_func: T.Callable[[argparse.Namespace], int], help_msg: str, aliases: T.List[str] = None) -> None:
+                    run_func: T.Callable[[argparse.Namespace], int], help_msg: str,
+                    aliases: T.List[str] | None = None) -> None:
         aliases = aliases or []
         # FIXME: Cannot have hidden subparser:
         # https://bugs.python.org/issue22848
@@ -185,7 +186,7 @@ class CommandLineParser:
             command = None
 
         from . import mesonlib
-        args = mesonlib.expand_arguments(args)
+        args = mesonlib.unwrap_err(mesonlib.expand_arguments(args), 'Failed to expand arguments')
         options = T.cast('MesonMainCMDOptions', parser.parse_args(args))
 
         if command is None:
diff --git a/mesonbuild/scripts/env2mfile.py b/mesonbuild/scripts/env2mfile.py
index ee973a923..2703bdde9 100755
--- a/mesonbuild/scripts/env2mfile.py
+++ b/mesonbuild/scripts/env2mfile.py
@@ -537,7 +537,7 @@ class AndroidDetector:
                 ofile.write("endian = 'little'\n")
 
 
-def run(options: T.Any) -> None:
+def run(options: argparse.Namespace) -> int:
     mlog.notice('This functionality is experimental and subject to change.')
     if options.cross:
         if options.use_for_build:
@@ -554,3 +554,5 @@ def run(options: T.Any) -> None:
         ad.detect_toolchains()
     else:
         raise ValueError("Encountered unreachable code-path")
+
+    return 0
diff --git a/mesonbuild/scripts/reprotest.py b/mesonbuild/scripts/reprotest.py
index fc9315c8f..ef9a4cb72 100755
--- a/mesonbuild/scripts/reprotest.py
+++ b/mesonbuild/scripts/reprotest.py
@@ -114,10 +114,10 @@ class ReproTester:
         self.check_contents('buildrepro', 'buildrepro.1st', True)
         self.check_contents('buildrepro.1st', 'buildrepro', False)
 
-def run(options: T.Any) -> None:
+def run(options: argparse.Namespace) -> int:
     rt = ReproTester(options)
     try:
-        sys.exit(rt.run())
+        return rt.run()
     except Exception as e:
         print(e)
-        sys.exit(1)
+        return 1