diff --git a/sys/contrib/dev/acpica/hwsleep.c b/sys/contrib/dev/acpica/hwsleep.c
index cc4aae2761d..494d37dd3dd 100644
--- a/sys/contrib/dev/acpica/hwsleep.c
+++ b/sys/contrib/dev/acpica/hwsleep.c
@@ -298,8 +298,10 @@ AcpiEnterSleepState (
     /* wait a second, then try again */
     AcpiOsStall(1000000);
 
-    AcpiHwRegisterWrite(ACPI_MTX_LOCK, PM1_CONTROL,
-        (1 << AcpiHwGetBitShift (SLP_EN_MASK)));
+    if (SleepState > ACPI_STATE_S1) {
+	AcpiHwRegisterWrite(ACPI_MTX_LOCK, PM1_CONTROL,
+	    (1 << AcpiHwGetBitShift (SLP_EN_MASK)));
+    }
 
     enable();