diff --git a/libcxx/include/__config b/libcxx/include/__config
--- a/libcxx/include/__config
+++ b/libcxx/include/__config
@@ -312,6 +312,14 @@
 #  define _LIBCPP_SHORT_WCHAR   1
 #endif
 
+#if defined(_AIX) || (defined(__MVS__) && defined(__64BIT__))
+// On AIX and zOS in 64-bit, wint_t is not able to represent any wchar_t value as well as WEOF
+// because wint_t and wchar_t have the same size, consequently an additional member is 
+// needed to indicate if the fill value is initialized.
+// Enabled in 32-bit for compatibility with the IBM AIX provided libc++.
+#  define _LIBCPP_BASIC_IOS_HAS_FILL_SET 1
+#endif
+
 // Libc++ supports various implementations of std::random_device.
 //
 // _LIBCPP_USING_DEV_RANDOM
diff --git a/libcxx/include/ios b/libcxx/include/ios
--- a/libcxx/include/ios
+++ b/libcxx/include/ios
@@ -680,6 +680,9 @@
 private:
     basic_ostream<char_type, traits_type>* __tie_;
     mutable int_type __fill_;
+#if defined(_LIBCPP_BASIC_IOS_HAS_FILL_SET)
+    mutable bool __fill_set_;
+#endif
 };
 
 template <class _CharT, class _Traits>
@@ -702,6 +705,9 @@
     ios_base::init(__sb);
     __tie_ = nullptr;
     __fill_ = traits_type::eof();
+#if defined(_LIBCPP_BASIC_IOS_HAS_FILL_SET)
+    __fill_set_ = false;
+#endif
 }
 
 template <class _CharT, class _Traits>
@@ -774,7 +780,17 @@
 basic_ios<_CharT, _Traits>::fill() const
 {
     if (traits_type::eq_int_type(traits_type::eof(), __fill_))
+    {
+#if defined(_LIBCPP_BASIC_IOS_HAS_FILL_SET)
+        if (!__fill_set_)
+        {
+            __fill_set_ = true;
+            __fill_ = widen(' ');
+        }
+#else
         __fill_ = widen(' ');
+#endif
+    }
     return __fill_;
 }
 
@@ -783,9 +799,7 @@
 _CharT
 basic_ios<_CharT, _Traits>::fill(char_type __ch)
 {
-    if (traits_type::eq_int_type(traits_type::eof(), __fill_))
-        __fill_ = widen(' ');
-    char_type __r = __fill_;
+    char_type __r = fill();
     __fill_ = __ch;
     return __r;
 }
@@ -800,6 +814,9 @@
         ios_base::copyfmt(__rhs);
         __tie_ = __rhs.__tie_;
         __fill_ = __rhs.__fill_;
+#if defined(_LIBCPP_BASIC_IOS_HAS_FILL_SET)
+        __fill_set_ = __rhs.__fill_set_;
+#endif
         __call_callbacks(copyfmt_event);
         exceptions(__rhs.exceptions());
     }
@@ -815,6 +832,9 @@
     __tie_ = __rhs.__tie_;
     __rhs.__tie_ = nullptr;
     __fill_ = __rhs.__fill_;
+#if defined(_LIBCPP_BASIC_IOS_HAS_FILL_SET)
+    __fill_set_ = __rhs.__fill_set_;
+#endif
 }
 
 template <class _CharT, class _Traits>
@@ -825,6 +845,9 @@
     ios_base::swap(__rhs);
     _VSTD::swap(__tie_, __rhs.__tie_);
     _VSTD::swap(__fill_, __rhs.__fill_);
+#if defined(_LIBCPP_BASIC_IOS_HAS_FILL_SET)
+    _VSTD::swap(__fill_set_, __rhs.__fill_set_);
+#endif
 }
 
 template <class _CharT, class _Traits>
diff --git a/libcxx/test/std/input.output/iostream.format/std.manip/setfill_wcharmax.pass.cpp b/libcxx/test/std/input.output/iostream.format/std.manip/setfill_wcharmax.pass.cpp
new file mode 100644
--- /dev/null
+++ b/libcxx/test/std/input.output/iostream.format/std.manip/setfill_wcharmax.pass.cpp
@@ -0,0 +1,45 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+// XFAIL: stdlib=libc++ && target=aarch64-linux-gnu
+// XFAIL: stdlib=libc++ && target=armv7l-linux-gnueabihf
+// XFAIL: stdlib=libc++ && target=armv8l-linux-gnueabihf
+// XFAIL: stdlib=libc++ && target=x86_64-pc-windows-msvc
+// XFAIL: stdlib=libc++ && target=x86_64-w64-windows-gnu
+
+// <iomanip>
+
+// template<charT> T4 setfill(charT c);
+
+#include <iomanip>
+#include <ostream>
+#include <cassert>
+#include <limits>
+
+#include "test_macros.h"
+
+template <class CharT>
+struct testbuf
+    : public std::basic_streambuf<CharT>
+{
+    testbuf() {}
+};
+
+int main(int, char**)
+{
+#ifndef TEST_HAS_NO_WIDE_CHARACTERS
+    {
+        testbuf<wchar_t> sb;
+        std::wostream os(&sb);
+        os << std::setfill(std::numeric_limits<wchar_t>::max());
+        assert(os.fill() == std::numeric_limits<wchar_t>::max());
+    }
+#endif
+
+  return 0;
+}