diff --git a/include/unistd.h b/include/unistd.h
index e15fa0e..16a8815 100644
--- a/include/unistd.h
+++ b/include/unistd.h
@@ -171,8 +171,6 @@ extern int __libc_pause (void);
 /* Not cancelable variant.  */
 extern int __pause_nocancel (void) attribute_hidden;
 
-extern int __have_dup3 attribute_hidden;
-
 extern int __getlogin_r_loginuid (char *name, size_t namesize)
      attribute_hidden;
 
diff --git a/libio/freopen.c b/libio/freopen.c
index 03e3ae7..ad1c848 100644
--- a/libio/freopen.c
+++ b/libio/freopen.c
@@ -78,32 +78,9 @@ freopen (const char *filename, const char *mode, FILE *fp)
 
       if (fd != -1)
 	{
-#ifdef O_CLOEXEC
-# ifndef __ASSUME_DUP3
-	  int newfd;
-	  if (__have_dup3 < 0)
-	    newfd = -1;
-	  else
-	    newfd =
-# endif
-	      __dup3 (_IO_fileno (result), fd,
-                      (result->_flags2 & _IO_FLAGS2_CLOEXEC) != 0
-                      ? O_CLOEXEC : 0);
-#else
-# define newfd 1
-#endif
-
-#ifndef __ASSUME_DUP3
-	  if (newfd < 0)
-	    {
-	      if (errno == ENOSYS)
-		__have_dup3 = -1;
-
-	      __dup2 (_IO_fileno (result), fd);
-	      if ((result->_flags2 & _IO_FLAGS2_CLOEXEC) != 0)
-		__fcntl (fd, F_SETFD, FD_CLOEXEC);
-	    }
-#endif
+	  __dup3 (_IO_fileno (result), fd,
+		  (result->_flags2 & _IO_FLAGS2_CLOEXEC) != 0
+		  ? O_CLOEXEC : 0);
 	  __close (_IO_fileno (result));
 	  _IO_fileno (result) = fd;
 	}
diff --git a/libio/freopen64.c b/libio/freopen64.c
index 1f0d8ab..adf749a 100644
--- a/libio/freopen64.c
+++ b/libio/freopen64.c
@@ -61,32 +61,9 @@ freopen64 (const char *filename, const char *mode, FILE *fp)
 
       if (fd != -1)
 	{
-#ifdef O_CLOEXEC
-# ifndef __ASSUME_DUP3
-	  int newfd;
-	  if (__have_dup3 < 0)
-	    newfd = -1;
-	  else
-	    newfd =
-# endif
-	      __dup3 (_IO_fileno (result), fd,
-                      (result->_flags2 & _IO_FLAGS2_CLOEXEC) != 0
-                      ? O_CLOEXEC : 0);
-#else
-# define newfd 1
-#endif
-
-#ifndef __ASSUME_DUP3
-	  if (newfd < 0)
-	    {
-	      if (errno == ENOSYS)
-		__have_dup3 = -1;
-
-	      __dup2 (_IO_fileno (result), fd);
-	      if ((result->_flags2 & _IO_FLAGS2_CLOEXEC) != 0)
-		__fcntl (fd, F_SETFD, FD_CLOEXEC);
-	    }
-#endif
+	  __dup3 (_IO_fileno (result), fd,
+		  (result->_flags2 & _IO_FLAGS2_CLOEXEC) != 0
+		  ? O_CLOEXEC : 0);
 	  __close (_IO_fileno (result));
 	  _IO_fileno (result) = fd;
 	}
diff --git a/socket/Makefile b/socket/Makefile
index c299d34..25d4f68 100644
--- a/socket/Makefile
+++ b/socket/Makefile
@@ -31,6 +31,6 @@ routines := accept bind connect getpeername getsockname getsockopt	\
 	    setsockopt shutdown socket socketpair isfdtype opensock	\
 	    sockatmark accept4 recvmmsg sendmmsg
 
-aux	 := have_sock_cloexec sa_len
+aux	 := sa_len
 
 include ../Rules
diff --git a/socket/have_sock_cloexec.c b/socket/have_sock_cloexec.c
deleted file mode 100644
index 579577d..0000000
--- a/socket/have_sock_cloexec.c
+++ /dev/null
@@ -1,24 +0,0 @@
-/* Copyright (C) 2008-2017 Free Software Foundation, Inc.
-   This file is part of the GNU C Library.
-
-   The GNU C Library is free software; you can redistribute it and/or
-   modify it under the terms of the GNU Lesser General Public
-   License as published by the Free Software Foundation; either
-   version 2.1 of the License, or (at your option) any later version.
-
-   The GNU C Library is distributed in the hope that it will be useful,
-   but WITHOUT ANY WARRANTY; without even the implied warranty of
-   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
-   Lesser General Public License for more details.
-
-   You should have received a copy of the GNU Lesser General Public
-   License along with the GNU C Library; if not, see
-   <http://www.gnu.org/licenses/>.  */
-
-#include <fcntl.h>
-#include <sys/socket.h>
-#include <kernel-features.h>
-
-#if defined O_CLOEXEC && !defined __ASSUME_DUP3
-int __have_dup3;
-#endif
diff --git a/sysdeps/mach/hurd/kernel-features.h b/sysdeps/mach/hurd/kernel-features.h
index 687c7f0..60c5bca 100644
--- a/sysdeps/mach/hurd/kernel-features.h
+++ b/sysdeps/mach/hurd/kernel-features.h
@@ -21,5 +21,4 @@
    But those referring to POSIX-level features like O_* flags can be.  */
 
 #define __ASSUME_O_CLOEXEC	1
-#define __ASSUME_DUP3		1
 #define __ASSUME_ACCEPT4	1
diff --git a/sysdeps/nacl/kernel-features.h b/sysdeps/nacl/kernel-features.h
index 38a47f1..4a5808b 100644
--- a/sysdeps/nacl/kernel-features.h
+++ b/sysdeps/nacl/kernel-features.h
@@ -23,6 +23,5 @@
 #define __ASSUME_O_CLOEXEC	1
 
 /*
-#define __ASSUME_DUP3		1
 #define __ASSUME_ACCEPT4	1
 */
diff --git a/sysdeps/unix/sysv/linux/kernel-features.h b/sysdeps/unix/sysv/linux/kernel-features.h
index 233e302..e0eb4e2 100644
--- a/sysdeps/unix/sysv/linux/kernel-features.h
+++ b/sysdeps/unix/sysv/linux/kernel-features.h
@@ -74,7 +74,6 @@
 /* Support for various CLOEXEC and NONBLOCK flags was added in
    2.6.27.  */
 #define __ASSUME_IN_NONBLOCK	1
-#define __ASSUME_DUP3		1
 
 /* Support for accept4 functionality was added in 2.6.28, but for some
    architectures using a separate syscall rather than socketcall that
