diff --git a/libcxx/include/__config b/libcxx/include/__config
--- a/libcxx/include/__config
+++ b/libcxx/include/__config
@@ -334,6 +334,15 @@
 #    define _LIBCPP_SHORT_WCHAR 1
 #  endif
 
+#  if _LIBCPP_ABI_VERSION < 2
+#    if defined(_AIX) || (defined(__MVS__) && defined(__64BIT__))
+#      define _LIBCPP_BASIC_IOS_HAS_FILL_SET 1
+#    elif defined(_WIN32) || defined(__APPLE__) || defined(__sun__) || defined(__linux__) || defined(__FreeBSD__) ||   \
+        defined(__NetBSD__) || defined(__OpenBSD__)
+#      define _LIBCPP_BASIC_IOS_HAS_FILL_SET 0
+#    endif
+#  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
@@ -686,7 +686,15 @@
     void set_rdbuf(basic_streambuf<char_type, traits_type>* __sb);
 private:
     basic_ostream<char_type, traits_type>* __tie_;
+
+#if defined(_LIBCPP_BASIC_IOS_HAS_FILL_SET)
+    static const bool __has_fill_set = _LIBCPP_BASIC_IOS_HAS_FILL_SET;
+#else
+    static const bool __has_fill_set = sizeof(char_type) >= sizeof(int_type);
+#endif
+
     mutable int_type __fill_;
+    mutable bool __fill_set_[__has_fill_set];
 };
 
 template <class _CharT, class _Traits>
@@ -708,7 +716,11 @@
 {
     ios_base::init(__sb);
     __tie_ = nullptr;
-    __fill_ = traits_type::eof();
+    if (__has_fill_set) {
+      __fill_set_[0] = false;
+    } else {
+      __fill_ = traits_type::eof();
+    }
 }
 
 template <class _CharT, class _Traits>
@@ -780,9 +792,15 @@
 _CharT
 basic_ios<_CharT, _Traits>::fill() const
 {
-    if (traits_type::eq_int_type(traits_type::eof(), __fill_))
-        __fill_ = widen(' ');
-    return __fill_;
+  if (__has_fill_set) {
+    if (!__fill_set_[0]) {
+      __fill_        = widen(' ');
+      __fill_set_[0] = true;
+    }
+  } else if (traits_type::eq_int_type(traits_type::eof(), __fill_)) {
+    __fill_ = widen(' ');
+  }
+  return __fill_;
 }
 
 template <class _CharT, class _Traits>
@@ -790,11 +808,9 @@
 _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_;
-    __fill_ = __ch;
-    return __r;
+  char_type __r = fill();
+  __fill_       = __ch;
+  return __r;
 }
 
 template <class _CharT, class _Traits>
@@ -807,6 +823,9 @@
         ios_base::copyfmt(__rhs);
         __tie_ = __rhs.__tie_;
         __fill_ = __rhs.__fill_;
+        if (__has_fill_set) {
+          __fill_set_[0] = __rhs.__fill_set_[0];
+        }
         __call_callbacks(copyfmt_event);
         exceptions(__rhs.exceptions());
     }
@@ -822,6 +841,9 @@
     __tie_ = __rhs.__tie_;
     __rhs.__tie_ = nullptr;
     __fill_ = __rhs.__fill_;
+    if (__has_fill_set) {
+      __fill_set_[0] = __rhs.__fill_set_[0];
+    }
 }
 
 template <class _CharT, class _Traits>
@@ -832,6 +854,9 @@
     ios_base::swap(__rhs);
     _VSTD::swap(__tie_, __rhs.__tie_);
     _VSTD::swap(__fill_, __rhs.__fill_);
+    if (__has_fill_set) {
+      _VSTD::swap(__fill_set_[0], __rhs.__fill_set_[0]);
+    }
 }
 
 template <class _CharT, class _Traits>
diff --git a/libcxx/test/std/input.output/iostream.format/std.manip/setfill_eof.pass.cpp b/libcxx/test/std/input.output/iostream.format/std.manip/setfill_eof.pass.cpp
new file mode 100644
--- /dev/null
+++ b/libcxx/test/std/input.output/iostream.format/std.manip/setfill_eof.pass.cpp
@@ -0,0 +1,37 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+// Test that weof as a wchar_t value can be set as the fill character.
+
+// UNSUPPORTED: no-wide-characters
+// REQUIRES: target=powerpc{{(64)?}}-ibm-aix || target=s390x-ibm-zos
+
+// <iomanip>
+
+// template<charT> unspecified setfill(charT c);
+
+#include <iomanip>
+#include <ostream>
+#include <cassert>
+#include <string>
+
+#include "test_macros.h"
+
+template <class CharT>
+struct testbuf : public std::basic_streambuf<CharT> {
+  testbuf() {}
+};
+
+int main(int, char**) {
+  testbuf<wchar_t> sb;
+  std::wostream os(&sb);
+  os << std::setfill((wchar_t)std::char_traits<wchar_t>::eof());
+  assert(os.fill() == (wchar_t)std::char_traits<wchar_t>::eof());
+
+  return 0;
+}