--- kernel/machdep/ppc/pmap.c	2018/04/24 18:26:08	1.1.1.1
+++ kernel/machdep/ppc/pmap.c	2018/04/24 18:32:53	1.1.1.2
@@ -1467,6 +1467,8 @@ pmap_enter(
 	/* if wired status has changed, update stats and change bit */
 	if (was_wired != wired) {
 		pmap->stats.wired_count += wired ? 1 : -1;
+		if (wired && pmap->stats.wired_count == 0)
+			panic("pmap_enter: wired_count");
 		mp->vm_info.bits.wired = wired;
 #if DEBUG
 		if (pmdebug & (PDB_WIRED))
@@ -1554,7 +1556,8 @@ pmap_change_wiring(
 	waswired = mp->vm_info.bits.wired;
 	if (wired && !waswired) {
 		mp->vm_info.bits.wired = TRUE;
-		pmap->stats.wired_count++;
+		if (++pmap->stats.wired_count == 0)
+			panic("pmap_change_wiring: wired_count");
 	} else if (!wired && waswired) {
 		mp->vm_info.bits.wired = FALSE;
 		pmap->stats.wired_count--;