diff --git a/Include/fileutils.h b/Include/fileutils.h
index 1d8df15..a232460 100644
--- a/Include/fileutils.h
+++ b/Include/fileutils.h
@@ -41,7 +41,8 @@
 #ifdef HAVE_REALPATH
 PyAPI_FUNC(wchar_t*) _Py_wrealpath(
     const wchar_t *path,
-    wchar_t *resolved_path);
+    wchar_t *resolved_path,
+    size_t resolved_path_size);
 #endif
 
 PyAPI_FUNC(wchar_t*) _Py_wgetcwd(