gcc: error: '__SIZEOF_WCHAR_T__' undeclared

Index: src/args.c
--- src/args.c.orig
+++ src/args.c
@@ -298,7 +298,7 @@ print_info(void)
 
 #endif
 
-	fprintf(stdout, "wchar_t width: %d, max: %d\n", __SIZEOF_WCHAR_T__, __WCHAR_MAX__);
+	fprintf(stdout, "wchar_t width: %zu, max: %d\n", sizeof(wchar_t), __WCHAR_MAX__);
 
 #if NCURSES_EXT_FUNCS