diff --git a/include/minix/callnr.h b/include/minix/callnr.h
index e8bd7a8d6..51c9103c9 100644
--- a/include/minix/callnr.h
+++ b/include/minix/callnr.h
@@ -103,10 +103,6 @@
 /* Field names for the setsid(2) call. */
 #define PM_GETSID_PID		m1_i1	/* pid_t */
 
-/* Field names for the setgroups(2)/setgroups(2) calls. */
-#define PM_GROUPS_NUM		m1_i1	/* int */
-#define PM_GROUPS_PTR		m1_p1	/* gid_t * */
-
 /* Field names for the getmcontext(2)/setmcontext(2) calls. */
 #define PM_MCONTEXT_CTX		m1_p1	/* mcontext_t * */
 
diff --git a/include/minix/ipc.h b/include/minix/ipc.h
index 421380efb..77c854a6d 100644
--- a/include/minix/ipc.h
+++ b/include/minix/ipc.h
@@ -145,6 +145,14 @@ typedef struct {
 } mess_sigcalls;
 _ASSERT_MSG_SIZE(mess_sigcalls);
 
+typedef struct {
+	int num;
+	vir_bytes ptr;		/* gid_t * */
+
+	uint8_t padding[48];
+} mess_lc_pm_groups;
+_ASSERT_MSG_SIZE(mess_lc_pm_groups);
+
 typedef struct {
 	int which;
 	vir_bytes value;	/* const struct itimerval * */
@@ -1000,6 +1008,7 @@ typedef struct {
 		mess_fs_vfs_readsuper	m_fs_vfs_readsuper;
 		mess_fs_vfs_readwrite	m_fs_vfs_readwrite;
 
+		mess_lc_pm_groups	m_lc_pm_groups;
 		mess_lc_pm_itimer	m_lc_pm_itimer;
 		mess_lc_pm_priority	m_lc_pm_priority;
 		mess_lc_pm_ptrace	m_lc_pm_ptrace;
diff --git a/lib/libc/sys-minix/getgroups.c b/lib/libc/sys-minix/getgroups.c
index edda7e08e..e1c6f5e81 100644
--- a/lib/libc/sys-minix/getgroups.c
+++ b/lib/libc/sys-minix/getgroups.c
@@ -14,8 +14,8 @@ int getgroups(int ngroups, gid_t *arr)
   message m;
 
   memset(&m, 0, sizeof(m));
-  m.PM_GROUPS_NUM = ngroups;
-  m.PM_GROUPS_PTR = (char *) arr;
+  m.m_lc_pm_groups.num = ngroups;
+  m.m_lc_pm_groups.ptr = (vir_bytes)arr;
 
   return(_syscall(PM_PROC_NR, PM_GETGROUPS, &m));
 }
diff --git a/lib/libc/sys-minix/setgroups.c b/lib/libc/sys-minix/setgroups.c
index c5aab68c4..ed5ac47d0 100644
--- a/lib/libc/sys-minix/setgroups.c
+++ b/lib/libc/sys-minix/setgroups.c
@@ -10,8 +10,8 @@ int setgroups(int ngroups, const gid_t *gidset)
   message m;
 
   memset(&m, 0, sizeof(m));
-  m.PM_GROUPS_PTR = (char *) __UNCONST(gidset);
-  m.PM_GROUPS_NUM = ngroups;
+  m.m_lc_pm_groups.ptr = (vir_bytes)gidset;
+  m.m_lc_pm_groups.num = ngroups;
 
   return(_syscall(PM_PROC_NR, PM_SETGROUPS, &m));
 }
diff --git a/servers/pm/getset.c b/servers/pm/getset.c
index 347213ebc..b6a21e0fc 100644
--- a/servers/pm/getset.c
+++ b/servers/pm/getset.c
@@ -26,7 +26,7 @@ int do_get()
 
   switch(call_nr) {
 	case PM_GETGROUPS:
-		ngroups = m_in.PM_GROUPS_NUM;
+		ngroups = m_in.m_lc_pm_groups.num;
 		if (ngroups > NGROUPS_MAX || ngroups < 0)
 			return(EINVAL);
 
@@ -40,8 +40,7 @@ int do_get()
 			return(EINVAL);
 
 		r = sys_datacopy(SELF, (vir_bytes) rmp->mp_sgroups, who_e,
-			(vir_bytes) m_in.PM_GROUPS_PTR,
-			ngroups * sizeof(gid_t));
+			m_in.m_lc_pm_groups.ptr, ngroups * sizeof(gid_t));
 
 		if (r != OK)
 			return(r);
@@ -140,15 +139,15 @@ int do_set()
 		if (rmp->mp_effuid != SUPER_USER)
 			return(EPERM);
 
-		ngroups = m_in.PM_GROUPS_NUM;
+		ngroups = m_in.m_lc_pm_groups.num;
 
 		if (ngroups > NGROUPS_MAX || ngroups < 0) 
 			return(EINVAL);
 
-		if (ngroups > 0 && m_in.PM_GROUPS_PTR == NULL)
+		if (ngroups > 0 && m_in.m_lc_pm_groups.ptr == 0)
 			return(EFAULT);
 
-		r = sys_datacopy(who_e, (vir_bytes) m_in.PM_GROUPS_PTR, SELF,
+		r = sys_datacopy(who_e, m_in.m_lc_pm_groups.ptr, SELF,
 			     (vir_bytes) rmp->mp_sgroups,
 			     ngroups * sizeof(gid_t));
 		if (r != OK)