diff --git a/include/minix/callnr.h b/include/minix/callnr.h
index 51c9103c9..7a4031149 100644
--- a/include/minix/callnr.h
+++ b/include/minix/callnr.h
@@ -106,9 +106,6 @@
 /* Field names for the getmcontext(2)/setmcontext(2) calls. */
 #define PM_MCONTEXT_CTX		m1_p1	/* mcontext_t * */
 
-/* Field names for the reboot(2) call. */
-#define PM_REBOOT_HOW		m1_i1	/* int */
-
 /*===========================================================================*
  *				Calls to VFS				     *
  *===========================================================================*/
diff --git a/include/minix/ipc.h b/include/minix/ipc.h
index 77c854a6d..03463e7ef 100644
--- a/include/minix/ipc.h
+++ b/include/minix/ipc.h
@@ -188,6 +188,13 @@ typedef struct {
 } mess_pm_lc_ptrace;
 _ASSERT_MSG_SIZE(mess_pm_lc_ptrace);
 
+typedef struct {
+	int how;
+
+	uint8_t padding[52];
+} mess_lc_pm_reboot;
+_ASSERT_MSG_SIZE(mess_lc_pm_reboot);
+
 typedef struct {
 	int req;
 	int field;
@@ -1012,6 +1019,7 @@ typedef struct {
 		mess_lc_pm_itimer	m_lc_pm_itimer;
 		mess_lc_pm_priority	m_lc_pm_priority;
 		mess_lc_pm_ptrace	m_lc_pm_ptrace;
+		mess_lc_pm_reboot	m_lc_pm_reboot;
 		mess_lc_pm_sysuname	m_lc_pm_sysuname;
 		mess_lc_pm_time		m_lc_pm_time;
 		mess_lc_pm_waitpid	m_lc_pm_waitpid;
diff --git a/lib/libc/sys-minix/reboot.c b/lib/libc/sys-minix/reboot.c
index 08a503e92..54cf580ed 100644
--- a/lib/libc/sys-minix/reboot.c
+++ b/lib/libc/sys-minix/reboot.c
@@ -16,6 +16,6 @@ int reboot(int how, char *bootstr)
   message m;
 
   memset(&m, 0, sizeof(m));
-  m.PM_REBOOT_HOW = how;
+  m.m_lc_pm_reboot.how = how;
   return _syscall(PM_PROC_NR, PM_REBOOT, &m);
 }
diff --git a/servers/pm/misc.c b/servers/pm/misc.c
index 8c1d32b54..8649ad639 100644
--- a/servers/pm/misc.c
+++ b/servers/pm/misc.c
@@ -211,7 +211,7 @@ int do_reboot()
   if (mp->mp_effuid != SUPER_USER) return(EPERM);
 
   /* See how the system should be aborted. */
-  abort_flag = (unsigned) m_in.PM_REBOOT_HOW;
+  abort_flag = m_in.m_lc_pm_reboot.how;
 
   /* notify readclock (some arm systems power off via RTC alarms) */
   if (abort_flag & RB_POWERDOWN) {