diff --git a/include/minix/callnr.h b/include/minix/callnr.h
index 93da5ada7..603068788 100644
--- a/include/minix/callnr.h
+++ b/include/minix/callnr.h
@@ -61,13 +61,6 @@
 
 #define NR_PM_CALLS		48	/* highest number from base plus one */
 
-/* Field names for the kill(2), srv_kill(2), and sigaction(2) calls. */
-#define PM_SIG_PID		m1_i1	/* pid_t */
-#define PM_SIG_NR		m1_i2	/* int */
-#define PM_SIG_ACT		m1_p1	/* const struct sigaction * */
-#define PM_SIG_OACT		m1_p2	/* struct sigaction * */
-#define PM_SIG_RET		m1_p3	/* int (*)(void) */
-
 /*===========================================================================*
  *				Calls to VFS				     *
  *===========================================================================*/
diff --git a/include/minix/ipc.h b/include/minix/ipc.h
index 55db51754..d0e94f07c 100644
--- a/include/minix/ipc.h
+++ b/include/minix/ipc.h
@@ -251,6 +251,17 @@ typedef struct {
 } mess_lc_pm_sysuname;
 _ASSERT_MSG_SIZE(mess_lc_pm_sysuname);
 
+typedef struct {
+	pid_t pid;
+	int nr;
+	vir_bytes act;		/* const struct sigaction * */
+	vir_bytes oact;		/* struct sigaction * */
+	vir_bytes ret;		/* int (*)(void) */
+
+	uint8_t padding[36];
+} mess_lc_pm_sig;
+_ASSERT_MSG_SIZE(mess_lc_pm_sig);
+
 typedef struct {
 	int how;
 	vir_bytes ctx;
@@ -1117,6 +1128,7 @@ typedef struct {
 		mess_lc_pm_reboot	m_lc_pm_reboot;
 		mess_lc_pm_setgid	m_lc_pm_setgid;
 		mess_lc_pm_setuid	m_lc_pm_setuid;
+		mess_lc_pm_sig		m_lc_pm_sig;
 		mess_lc_pm_sigset	m_lc_pm_sigset;
 		mess_lc_pm_sysuname	m_lc_pm_sysuname;
 		mess_lc_pm_time		m_lc_pm_time;
diff --git a/lib/libc/sys-minix/kill.c b/lib/libc/sys-minix/kill.c
index 367d2ef22..4bedfdd5f 100644
--- a/lib/libc/sys-minix/kill.c
+++ b/lib/libc/sys-minix/kill.c
@@ -16,7 +16,7 @@ int sig;			/* signal number */
   message m;
 
   memset(&m, 0, sizeof(m));
-  m.PM_SIG_PID = proc;
-  m.PM_SIG_NR = sig;
+  m.m_lc_pm_sig.pid = proc;
+  m.m_lc_pm_sig.nr = sig;
   return(_syscall(PM_PROC_NR, PM_KILL, &m));
 }
diff --git a/lib/libc/sys-minix/sigaction.c b/lib/libc/sys-minix/sigaction.c
index 7f006caf1..c01adaa45 100644
--- a/lib/libc/sys-minix/sigaction.c
+++ b/lib/libc/sys-minix/sigaction.c
@@ -12,10 +12,10 @@ int sigaction(int sig, const struct sigaction *act, struct sigaction *oact)
   message m;
 
   memset(&m, 0, sizeof(m));
-  m.PM_SIG_NR = sig;
-  m.PM_SIG_ACT = (char *) __UNCONST(act);
-  m.PM_SIG_OACT = (char *) oact;
-  m.PM_SIG_RET = (char *) __sigreturn;
+  m.m_lc_pm_sig.nr = sig;
+  m.m_lc_pm_sig.act = (vir_bytes)act;
+  m.m_lc_pm_sig.oact = (vir_bytes)oact;
+  m.m_lc_pm_sig.ret = (vir_bytes)__sigreturn;
 
   return(_syscall(PM_PROC_NR, PM_SIGACTION, &m));
 }
diff --git a/servers/pm/signal.c b/servers/pm/signal.c
index 115df742a..304fd6085 100644
--- a/servers/pm/signal.c
+++ b/servers/pm/signal.c
@@ -45,23 +45,23 @@ int do_sigaction(void)
 
   assert(!(mp->mp_flags & (PROC_STOPPED | VFS_CALL | UNPAUSED)));
 
-  sig_nr = m_in.PM_SIG_NR;
+  sig_nr = m_in.m_lc_pm_sig.nr;
   if (sig_nr == SIGKILL) return(OK);
   if (sig_nr < 1 || sig_nr >= _NSIG) return(EINVAL);
 
   svp = &mp->mp_sigact[sig_nr];
-  if ((struct sigaction *) m_in.PM_SIG_OACT != (struct sigaction *) NULL) {
+  if (m_in.m_lc_pm_sig.oact != 0) {
 	r = sys_datacopy(PM_PROC_NR,(vir_bytes) svp, who_e,
-		(vir_bytes) m_in.PM_SIG_OACT, (phys_bytes) sizeof(svec));
+		m_in.m_lc_pm_sig.oact, (phys_bytes) sizeof(svec));
 	if (r != OK) return(r);
   }
 
-  if ((struct sigaction *) m_in.PM_SIG_ACT == (struct sigaction *) NULL)
+  if (m_in.m_lc_pm_sig.act == 0)
   	return(OK);
 
   /* Read in the sigaction structure. */
-  r = sys_datacopy(who_e, (vir_bytes) m_in.PM_SIG_ACT,
-		PM_PROC_NR, (vir_bytes) &svec, (phys_bytes) sizeof(svec));
+  r = sys_datacopy(who_e, m_in.m_lc_pm_sig.act, PM_PROC_NR, (vir_bytes) &svec,
+	  (phys_bytes) sizeof(svec));
   if (r != OK) return(r);
 
   if (svec.sa_handler == SIG_IGN) {
@@ -81,7 +81,7 @@ int do_sigaction(void)
   sigdelset(&svec.sa_mask, SIGSTOP);
   mp->mp_sigact[sig_nr].sa_mask = svec.sa_mask;
   mp->mp_sigact[sig_nr].sa_flags = svec.sa_flags;
-  mp->mp_sigreturn = (vir_bytes) m_in.PM_SIG_RET;
+  mp->mp_sigreturn = m_in.m_lc_pm_sig.ret;
   return(OK);
 }
 
@@ -198,7 +198,7 @@ int do_kill(void)
 {
 /* Perform the kill(pid, signo) system call. */
 
-  return check_sig(m_in.PM_SIG_PID, m_in.PM_SIG_NR, FALSE /* ksig */);
+  return check_sig(m_in.m_lc_pm_sig.pid, m_in.m_lc_pm_sig.nr, FALSE /* ksig */);
 }
 
 /*===========================================================================*