diff --git a/libcxx/include/ios b/libcxx/include/ios
--- a/libcxx/include/ios
+++ b/libcxx/include/ios
@@ -678,6 +678,7 @@
 private:
     basic_ostream<char_type, traits_type>* __tie_;
     mutable int_type __fill_;
+    bool __fill_set;
 };
 
 template <class _CharT, class _Traits>
@@ -700,6 +701,7 @@
     ios_base::init(__sb);
     __tie_ = nullptr;
     __fill_ = traits_type::eof();
+    __fill_set = false;
 }
 
 template <class _CharT, class _Traits>
@@ -771,7 +773,7 @@
 _CharT
 basic_ios<_CharT, _Traits>::fill() const
 {
-    if (traits_type::eq_int_type(traits_type::eof(), __fill_))
+    if (!__fill_set && traits_type::eq_int_type(traits_type::eof(), __fill_))
         __fill_ = widen(' ');
     return __fill_;
 }
@@ -781,8 +783,11 @@
 _CharT
 basic_ios<_CharT, _Traits>::fill(char_type __ch)
 {
+    if (!__fill_set && traits_type::eq_int_type(traits_type::eof(), __fill_))
+        __fill_ = widen(' ');
     char_type __r = __fill_;
     __fill_ = __ch;
+    __fill_set = true;
     return __r;
 }
 
@@ -796,6 +801,7 @@
         ios_base::copyfmt(__rhs);
         __tie_ = __rhs.__tie_;
         __fill_ = __rhs.__fill_;
+	__fill_set = __rhs.__fill_set;
         __call_callbacks(copyfmt_event);
         exceptions(__rhs.exceptions());
     }
@@ -811,6 +817,7 @@
     __tie_ = __rhs.__tie_;
     __rhs.__tie_ = nullptr;
     __fill_ = __rhs.__fill_;
+    __fill_set = __rhs.__fill_set;
 }
 
 template <class _CharT, class _Traits>
@@ -821,6 +828,7 @@
     ios_base::swap(__rhs);
     _VSTD::swap(__tie_, __rhs.__tie_);
     _VSTD::swap(__fill_, __rhs.__fill_);
+    _VSTD::swap(__fill_set, __rhs.__fill_set);
 }
 
 template <class _CharT, class _Traits>
diff --git a/libcxx/test/std/input.output/iostreams.base/ios/basic.ios.members/fill_init.pass.cpp b/libcxx/test/std/input.output/iostreams.base/ios/basic.ios.members/fill_init.pass.cpp
new file mode 100644
--- /dev/null
+++ b/libcxx/test/std/input.output/iostreams.base/ios/basic.ios.members/fill_init.pass.cpp
@@ -0,0 +1,56 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+// <ios>
+
+// template <class charT, class traits> class basic_ios
+
+// char_type fill() const;
+// char_type fill(char_type fillch);
+
+// Make sure fill() returns the right initialized value of __fill_.
+
+#include <ios>
+#include <cassert>
+#include <string>
+
+#include "test_macros.h"
+
+int main(int, char**) {
+  {
+    std::basic_ios<char> ios(0);
+    assert(ios.fill() == ' ');
+  }
+  {
+    std::basic_ios<char> ios(0);
+    assert(ios.fill('x') == ' ');
+  }
+  {
+    std::basic_ios<char> ios(0);
+    ios.fill('x');
+    char ch = ios.fill(std::char_traits<char>::eof());
+    assert(ch == 'x');
+  }
+#ifndef TEST_HAS_NO_WIDE_CHARACTERS
+  {
+    std::basic_ios<wchar_t> ios(0);
+    assert(ios.fill() == ' ');
+  }
+  {
+    std::basic_ios<wchar_t> ios(0);
+    assert(ios.fill('x') == ' ');
+  }
+  {
+    std::basic_ios<wchar_t> ios(0);
+    ios.fill('x');
+    wchar_t ch = ios.fill(std::char_traits<wchar_t>::eof());
+    assert(ch == 'x');
+  }
+#endif
+  return 0;
+}