Index: glibc-2.23/sysdeps/mach/hurd/adjtime.c
===================================================================
--- glibc-2.23.orig/sysdeps/mach/hurd/adjtime.c
+++ glibc-2.23/sysdeps/mach/hurd/adjtime.c
@@ -28,16 +28,25 @@ __adjtime (const struct timeval *delta,
 {
   error_t err;
   mach_port_t hostpriv;
+  struct timeval dummy = {0, 0};
 
   err = __get_privileged_ports (&hostpriv, NULL);
   if (err)
     return __hurd_fail (EPERM);
 
-  err = __host_adjust_time (hostpriv,
-			    /* `time_value_t' and `struct timeval' are in
-                               fact identical with the names changed.  */
-			    *(time_value_t *) delta,
-			    (time_value_t *) olddelta);
+    if (olddelta)
+      err = __host_adjust_time (hostpriv,
+				/* `time_value_t' and `struct timeval' are in
+				   fact identical with the names changed.  */
+				*(time_value_t *) delta,
+				(time_value_t *) olddelta);
+    else
+      /* Handle the case when olddelta is NULL, see man adjtime(3) */
+      err = __host_adjust_time (hostpriv,
+				/* `time_value_t' and `struct timeval' are in
+				   fact identical with the names changed.  */
+				*(time_value_t *) delta,
+				(time_value_t *) &dummy);
   __mach_port_deallocate (__mach_task_self (), hostpriv);
 
   if (err)