diff --git a/ChangeLog b/ChangeLog
index 504de57b0e..36f1b00e95 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+2017-03-03  Justus Winter <justus@gnupg.org>
+
+	* sysdeps/mach/hurd/ftruncate64.c: New file.
+	* sysdeps/mach/hurd/truncate64.c: Likewise.
+
 2017-03-03  Florian Weimer  <fweimer@redhat.com>
 
 	* time/tzfile.c (NOID): Do not define.
diff --git a/sysdeps/mach/hurd/ftruncate64.c b/sysdeps/mach/hurd/ftruncate64.c
new file mode 100644
index 0000000000..53c4f64afc
--- /dev/null
+++ b/sysdeps/mach/hurd/ftruncate64.c
@@ -0,0 +1,34 @@
+/* Copyright (C) 1991-2017 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 <errno.h>
+#include <sys/types.h>
+#include <unistd.h>
+#include <hurd.h>
+#include <hurd/fd.h>
+
+/* Truncate the file referenced by FD to LENGTH bytes.  */
+int
+__ftruncate64 (int fd, off64_t length)
+{
+  error_t err;
+  if (err = HURD_DPORT_USE (fd, __file_set_size (port, length)))
+    return __hurd_dfail (fd, err);
+  return 0;
+}
+
+weak_alias (__ftruncate64, ftruncate64)
diff --git a/sysdeps/mach/hurd/truncate64.c b/sysdeps/mach/hurd/truncate64.c
new file mode 100644
index 0000000000..a2e2ed2190
--- /dev/null
+++ b/sysdeps/mach/hurd/truncate64.c
@@ -0,0 +1,42 @@
+/* Copyright (C) 1991-2017 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 <errno.h>
+#include <fcntl.h>
+#include <sys/types.h>
+#include <unistd.h>
+#include <hurd.h>
+
+/* Truncate FILE_NAME to LENGTH bytes.  */
+int
+__truncate64 (const char *file_name, off64_t length)
+{
+  error_t err;
+  file_t file = __file_name_lookup (file_name, O_WRITE, 0);
+
+  if (file == MACH_PORT_NULL)
+    return -1;
+
+  err = __file_set_size (file, length);
+  __mach_port_deallocate (__mach_task_self (), file);
+
+  if (err)
+    return __hurd_fail (err);
+  return 0;
+}
+
+weak_alias (__truncate64, truncate64)