diff --git a/sys/powerpc/powermac/powermac_thermal.c b/sys/powerpc/powermac/powermac_thermal.c
index 1b030729be9e..9c1f59d62221 100644
--- a/sys/powerpc/powermac/powermac_thermal.c
+++ b/sys/powerpc/powermac/powermac_thermal.c
@@ -109,9 +109,10 @@ pmac_therm_manage_fans(void)
 			printf("WARNING: Current temperature (%s: %d.%d C) "
 			    "exceeds critical temperature (%d.%d C)! "
 			    "Shutting down!\n", sensor->sensor->name,
-			    sensor->last_val / 10, sensor->last_val % 10,
-			    sensor->sensor->max_temp / 10,
-			    sensor->sensor->max_temp % 10);
+			       (sensor->last_val - ZERO_C_TO_K) / 10,
+			       (sensor->last_val - ZERO_C_TO_K) % 10,
+			       (sensor->sensor->max_temp - ZERO_C_TO_K) / 10,
+			       (sensor->sensor->max_temp - ZERO_C_TO_K) % 10);
 			shutdown_nice(RB_POWEROFF);
 		}
 	}
diff --git a/sys/powerpc/powermac/powermac_thermal.h b/sys/powerpc/powermac/powermac_thermal.h
index 43bd6295a6b6..424c6122f0ad 100644
--- a/sys/powerpc/powermac/powermac_thermal.h
+++ b/sys/powerpc/powermac/powermac_thermal.h
@@ -29,6 +29,8 @@
 #ifndef _POWERPC_POWERMAC_POWERMAC_THERMAL_H
 #define _POWERPC_POWERMAC_POWERMAC_THERMAL_H
 
+#define ZERO_C_TO_K 2732
+
 struct pmac_fan {
 	int min_rpm, max_rpm, default_rpm;