diff --git a/Tools/wasm/mypy.ini b/Tools/wasm/mypy.ini
index 176794bbb4d9a8a..c62598f89eba69e 100644
--- a/Tools/wasm/mypy.ini
+++ b/Tools/wasm/mypy.ini
@@ -10,6 +10,5 @@ python_version = 3.8
 strict = True
 enable_error_code = truthy-bool,ignore-without-code
 
-# except for a few settings that can't yet be enabled:
-warn_return_any = False
-warn_unreachable = False
+# except for incomplete defs, which are useful for module authors:
+disallow_incomplete_defs = False
diff --git a/Tools/wasm/wasm_assets.py b/Tools/wasm/wasm_assets.py
index 9acfa95f1c6dd1d..80cf285c75f0447 100755
--- a/Tools/wasm/wasm_assets.py
+++ b/Tools/wasm/wasm_assets.py
@@ -16,7 +16,7 @@
 import sys
 import sysconfig
 import zipfile
-from typing import Dict
+from typing import Dict, cast
 
 # source directory
 SRCDIR = pathlib.Path(__file__).parent.parent.parent.absolute()
@@ -111,7 +111,8 @@ def get_builddir(args: argparse.Namespace) -> pathlib.Path:
 
 def get_sysconfigdata(args: argparse.Namespace) -> pathlib.Path:
     """Get path to sysconfigdata relative to build root"""
-    data_name = sysconfig._get_sysconfigdata_name()  # type: ignore[attr-defined]
+    assert isinstance(args.builddir, pathlib.Path)
+    data_name: str = sysconfig._get_sysconfigdata_name()  # type: ignore[attr-defined]
     if not data_name.startswith(SYSCONFIG_NAMES):
         raise ValueError(
             f"Invalid sysconfig data name '{data_name}'.", SYSCONFIG_NAMES