diff --git a/sys/powerpc/powermac/pmu.c b/sys/powerpc/powermac/pmu.c
--- a/sys/powerpc/powermac/pmu.c
+++ b/sys/powerpc/powermac/pmu.c
@@ -964,7 +964,7 @@
 }
 
 static void
-pmu_battquery_proc()
+pmu_battquery_proc(void)
 {
 	struct pmu_softc *sc;
 	struct pmu_battstate batt;
@@ -977,8 +977,10 @@
 	while (1) {
 		kproc_suspend_check(curproc);
 		error = pmu_query_battery(sc, 0, &batt);
-		pmu_battery_notify(&batt, &cur_batt);
-		cur_batt = batt;
+		if (error == 0) {
+			pmu_battery_notify(&batt, &cur_batt);
+			cur_batt = batt;
+		}
 		pause("pmu_batt", hz);
 	}
 }