Index: libcxx/include/__locale
===================================================================
--- libcxx/include/__locale
+++ libcxx/include/__locale
@@ -712,9 +712,9 @@
     static locale::id id;
 
 #ifdef _CACHED_RUNES
-    static const size_t table_size = _CACHED_RUNES;
+    static _LIBCPP_CONSTEXPR const size_t table_size = _CACHED_RUNES;
 #else
-    static const size_t table_size = 256;  // FIXME: Don't hardcode this.
+    static _LIBCPP_CONSTEXPR const size_t table_size = 256;  // FIXME: Don't hardcode this.
 #endif
     _LIBCPP_INLINE_VISIBILITY const mask* table() const  _NOEXCEPT {return __tab_;}
     static const mask* classic_table()  _NOEXCEPT;
Index: libcxx/test/std/localization/locale.categories/category.ctype/facet.ctype.special/facet.ctype.char.statics/table_size.pass.cpp
===================================================================
--- /dev/null
+++ libcxx/test/std/localization/locale.categories/category.ctype/facet.ctype.special/facet.ctype.char.statics/table_size.pass.cpp
@@ -0,0 +1,27 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// <locale>
+
+// template <> class ctype<char>
+
+// UNSUPPORTED: c++03, c++11, c++14
+
+#include <locale>
+#include <cassert>
+
+#include "test_macros.h"
+
+int main(int, char**)
+{
+  typedef std::ctype<char> F;
+  const size_t *G = &F::table_size;
+  assert(*G >= 256);
+
+  return 0;
+}