diff --git a/external/gpl3/gcc/dist/libstdc++-v3/config/io/basic_file_stdio.cc b/external/gpl3/gcc/dist/libstdc++-v3/config/io/basic_file_stdio.cc
index 09fdd750b807..5717924944bc 100644
--- a/external/gpl3/gcc/dist/libstdc++-v3/config/io/basic_file_stdio.cc
+++ b/external/gpl3/gcc/dist/libstdc++-v3/config/io/basic_file_stdio.cc
@@ -204,7 +204,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
   { this->close(); }
 
   __basic_file<char>*
-  __basic_file<char>::sys_open(__c_file* __file, ios_base::openmode)
+  __basic_file<char>::sys_open(__c_file* __file, ios_base::openmode __mode)
   {
     __basic_file* __ret = NULL;
     if (!this->is_open() && __file)
@@ -213,7 +213,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 	// POSIX guarantees that fflush sets errno on error, but C doesn't.
 	errno = 0;
 	do
-	  __err = fflush(__file);
+	  __err = (__mode == std::ios_base::in ? 0 : fflush(__file));
 	while (__err && errno == EINTR);
 	errno = __save_errno;
 	if (!__err)
diff --git a/tests/lib/libstdc++/t_sync_with_stdio.sh b/tests/lib/libstdc++/t_sync_with_stdio.sh
index 9c1dfaf7018d..fe76c49b988f 100644
--- a/tests/lib/libstdc++/t_sync_with_stdio.sh
+++ b/tests/lib/libstdc++/t_sync_with_stdio.sh
@@ -1,4 +1,4 @@
-#	$NetBSD: t_sync_with_stdio.sh,v 1.1 2024/04/28 01:21:27 riastradh Exp $
+#	$NetBSD: t_sync_with_stdio.sh,v 1.2 2024/05/20 11:20:53 riastradh Exp $
 #
 # Copyright (c) 2024 The NetBSD Foundation, Inc.
 # All rights reserved.
@@ -32,7 +32,6 @@ cin_nosync_head()
 cin_nosync_body()
 {
 	echo hello >in
-	atf_expect_fail "PR lib/58206: sync_with_stdio breaks reads from cin"
 	atf_check -o inline:'6\n' "$(atf_get_srcdir)"/h_cin_nosync <in
 }