diff --git a/xarray/core/utils.py b/xarray/core/utils.py
index 3bbf06cf967..7111ebf2c0d 100644
--- a/xarray/core/utils.py
+++ b/xarray/core/utils.py
@@ -1248,7 +1248,12 @@ def find_stack_level(test_mode=False) -> int:
     pkg_dir = Path(xr.__file__).parent
     test_dir = pkg_dir / "tests"
 
-    std_lib_dir = Path(sys.modules["os"].__file__).parent  # Standard library path
+    std_lib_path = sys.modules["os"].__file__
+    # Mostly to appease mypy; I don't think this can happen...
+    if std_lib_path is None:
+        return 0
+
+    std_lib_dir = Path(std_lib_path).parent  # Standard library path
 
     frame = inspect.currentframe()
     n = 0