diff --git a/ChangeLog b/ChangeLog
index fdd7bf3081..bb2824c715 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,9 @@
+2018-11-19  Samuel Thibault  <samuel.thibault@ens-lyon.org>
+
+	* sysdeps/mach/hurd/f_setlk.c: Include <unistd.h>.
+	(__f_setlk): When whence is SEEK_CUR, use __lseek64 to convert it to
+	SEEK_SET.
+
 2018-11-19  Mao Han  <han_mao@c-sky.com>
 
 	* scripts/config.guess: Update to version 2018-08-29.
diff --git a/sysdeps/mach/hurd/f_setlk.c b/sysdeps/mach/hurd/f_setlk.c
index 718af67e32..edfb292dbf 100644
--- a/sysdeps/mach/hurd/f_setlk.c
+++ b/sysdeps/mach/hurd/f_setlk.c
@@ -19,6 +19,7 @@
 #include <sys/types.h>
 #include <sys/file.h>
 #include <fcntl.h>
+#include <unistd.h>
 #include <errno.h>
 
 /* XXX
@@ -45,6 +46,18 @@ __f_setlk (int fd, int type, int whence, __off64_t start, __off64_t len, int wai
   if (cmd != LOCK_UN && wait == 0)
     cmd |= LOCK_NB;
 
+  if (whence == SEEK_CUR)
+    {
+      /* In case the target position is 0, we can support it below.  */
+      __off64_t cur = __lseek64 (fd, 0, SEEK_CUR);
+
+      if (cur >= 0)
+	{
+	  start = cur + start;
+	  whence = SEEK_SET;
+	}
+    }
+
   switch (whence)
     {
     case SEEK_SET: