diff --git a/Modules/main.c b/Modules/main.c
index bbf695f..0c38fac 100644
--- a/Modules/main.c
+++ b/Modules/main.c
@@ -486,10 +486,12 @@
             /* Use utf-8 on Mac OS X */
             unicode = PyUnicode_FromString(p);
 #else
-            wchar_t *wchar = _Py_char2wchar(p);
+            wchar_t *wchar;
+            size_t len;
+            wchar = _Py_char2wchar(p, &len);
             if (wchar == NULL)
                 continue;
-            unicode = PyUnicode_FromWideChar(wchar, wcslen(wchar));
+            unicode = PyUnicode_FromWideChar(wchar, len);
             PyMem_Free(wchar);
 #endif
             if (unicode == NULL)