diff --git a/Python/errors.c b/Python/errors.c
index d5a6fae..a55233f 100644
--- a/Python/errors.c
+++ b/Python/errors.c
@@ -515,10 +515,14 @@ PyObject *PyErr_SetExcFromWindowsErrWithFilename(
     int ierr,
     const char *filename)
 {
-    PyObject *name = filename ? PyUnicode_FromString(filename) : NULL;
-    PyObject *ret = PyErr_SetExcFromWindowsErrWithFilenameObject(exc,
-                                                                 ierr,
-                                                                 name);
+    PyObject *name, *ret;
+
+    if (filename) {
+        Py_ssize_t size = Py_SAFE_DOWNCAST(strlen(s), size_t, Py_ssize_t);
+        name = PyUnicode_DecodeMBCS(filename, size, "ignore");
+    } else
+        name = NULL;
+    ret = PyErr_SetExcFromWindowsErrWithFilenameObject(exc, ierr, name);
     Py_XDECREF(name);
     return ret;
 }
@@ -552,10 +556,16 @@ PyObject *PyErr_SetFromWindowsErrWithFilename(
     int ierr,
     const char *filename)
 {
-    PyObject *name = filename ? PyUnicode_FromString(filename) : NULL;
-    PyObject *result = PyErr_SetExcFromWindowsErrWithFilenameObject(
-                                                  PyExc_WindowsError,
-                                                  ierr, name);
+    PyObject *name, *result;
+
+    if (filename) {
+        Py_ssize_t size = Py_SAFE_DOWNCAST(strlen(s), size_t, Py_ssize_t);
+        name = PyUnicode_DecodeMBCS(filename, size, "ignore");
+    } else
+        name = NULL;
+    result = PyErr_SetExcFromWindowsErrWithFilenameObject(
+                 PyExc_WindowsError,
+                 ierr, name);
     Py_XDECREF(name);
     return result;
 }