diff --git a/libcxx/include/__locale b/libcxx/include/__locale
--- a/libcxx/include/__locale
+++ b/libcxx/include/__locale
@@ -549,8 +549,10 @@
 
     _LIBCPP_INLINE_VISIBILITY ctype_base() {}
 
+#ifndef _NEWLIB_VERSION
     static_assert((__regex_word & ~(space | print | cntrl | upper | lower | alpha | digit | punct | xdigit | blank)) == __regex_word,
                   "__regex_word can't overlap other bits");
+#endif
 };
 
 template <class _CharT> class _LIBCPP_TEMPLATE_VIS ctype;