diff --git a/sys/dev/acpica/acpi.c b/sys/dev/acpica/acpi.c
--- a/sys/dev/acpica/acpi.c
+++ b/sys/dev/acpica/acpi.c
@@ -102,6 +102,11 @@
 	int		num;
 };
 
+struct acpi_wake_prep_context {
+    struct acpi_softc	*sc;
+    enum power_stype	stype;
+};
+
 static char *sysres_ids[] = { "PNP0C01", "PNP0C02", NULL };
 
 /* Global mutex for locking access to the ACPI subsystem. */
@@ -175,10 +180,11 @@
 static void	acpi_shutdown_final(void *arg, int howto);
 static void	acpi_enable_fixed_events(struct acpi_softc *sc);
 static void	acpi_resync_clock(struct acpi_softc *sc);
-static int	acpi_wake_sleep_prep(ACPI_HANDLE handle,
+static int	acpi_wake_sleep_prep(struct acpi_softc *sc, ACPI_HANDLE handle,
+		    enum power_stype stype);
+static int	acpi_wake_run_prep(struct acpi_softc *sc, ACPI_HANDLE handle,
 		    enum power_stype stype);
-static int	acpi_wake_run_prep(ACPI_HANDLE handle, enum power_stype stype);
-static int	acpi_wake_prep_walk(enum power_stype stype);
+static int	acpi_wake_prep_walk(struct acpi_softc *sc, enum power_stype stype);
 static int	acpi_wake_sysctl_walk(device_t dev);
 static int	acpi_wake_set_sysctl(SYSCTL_HANDLER_ARGS);
 static int	acpi_supported_sleep_state_sysctl(SYSCTL_HANDLER_ARGS);
@@ -865,6 +871,7 @@
 static int
 acpi_shutdown(device_t dev)
 {
+    struct acpi_softc *sc = device_get_softc(dev);
 
     bus_topo_assert();
 
@@ -875,7 +882,7 @@
      * Enable any GPEs that are able to power-on the system (i.e., RTC).
      * Also, disable any that are not valid for this state (most).
      */
-    acpi_wake_prep_walk(ACPI_STATE_S5);
+    acpi_wake_prep_walk(sc, POWER_STYPE_POWEROFF);
 
     return (0);
 }
@@ -3480,7 +3487,7 @@
     sc->acpi_stype = stype;
 
     /* Enable any GPEs as appropriate and requested by the user. */
-    acpi_wake_prep_walk(stype);
+    acpi_wake_prep_walk(sc, stype);
     slp_state = ACPI_SS_GPE_SET;
 
     /*
@@ -3582,7 +3589,7 @@
     if (slp_state >= ACPI_SS_SLP_PREP)
 	resumeclock();
     if (slp_state >= ACPI_SS_GPE_SET) {
-	acpi_wake_prep_walk(stype);
+	acpi_wake_prep_walk(sc, stype);
 	sc->acpi_stype = POWER_STYPE_AWAKE;
     }
     if (slp_state >= ACPI_SS_DEV_SUSPEND)
@@ -3674,19 +3681,18 @@
 }
 
 static int
-acpi_wake_sleep_prep(ACPI_HANDLE handle, enum power_stype stype)
+acpi_wake_sleep_prep(struct acpi_softc *sc, ACPI_HANDLE handle,
+    enum power_stype stype)
 {
     int sstate;
     struct acpi_prw_data prw;
     device_t dev;
-    struct acpi_softc *sc;
 
     /* Check that this is a wake-capable device and get its GPE. */
     if (acpi_parse_prw(handle, &prw) != 0)
 	return (ENXIO);
     dev = acpi_get_device(handle);
 
-    sc = device_get_softc(dev);
     sstate = acpi_stype_to_sstate(sc, stype);
 
     /*
@@ -3713,12 +3719,12 @@
 }
 
 static int
-acpi_wake_run_prep(ACPI_HANDLE handle, enum power_stype stype)
+acpi_wake_run_prep(struct acpi_softc *sc, ACPI_HANDLE handle,
+    enum power_stype stype)
 {
     int sstate;
     struct acpi_prw_data prw;
     device_t dev;
-    struct acpi_softc *sc;
 
     /*
      * Check that this is a wake-capable device and get its GPE.  Return
@@ -3730,7 +3736,6 @@
     if (dev == NULL || (acpi_get_flags(dev) & ACPI_FLAG_WAKE_ENABLED) == 0)
 	return (0);
 
-    sc = device_get_softc(dev);
     sstate = acpi_stype_to_sstate(sc, stype);
 
     /*
@@ -3756,26 +3761,30 @@
 static ACPI_STATUS
 acpi_wake_prep(ACPI_HANDLE handle, UINT32 level, void *context, void **status)
 {
-    enum power_stype stype;
+    struct acpi_softc *sc = ((struct acpi_wake_prep_context *)context)->sc;
+    enum power_stype stype = ((struct acpi_wake_prep_context *)context)->stype;
 
     /* If suspending, run the sleep prep function, otherwise wake. */
-    stype = *(enum power_stype *)context;
     if (AcpiGbl_SystemAwakeAndRunning)
-	acpi_wake_sleep_prep(handle, stype);
+	acpi_wake_sleep_prep(sc, handle, stype);
     else
-	acpi_wake_run_prep(handle, stype);
+	acpi_wake_run_prep(sc, handle, stype);
     return (AE_OK);
 }
 
 /* Walk the tree rooted at acpi0 to prep devices for suspend/resume. */
 static int
-acpi_wake_prep_walk(enum power_stype stype)
+acpi_wake_prep_walk(struct acpi_softc *sc, enum power_stype stype)
 {
     ACPI_HANDLE sb_handle;
+    struct acpi_wake_prep_context ctx = {
+	.sc = sc,
+	.stype = stype,
+    };
 
     if (ACPI_SUCCESS(AcpiGetHandle(ACPI_ROOT_OBJECT, "\\_SB_", &sb_handle)))
 	AcpiWalkNamespace(ACPI_TYPE_DEVICE, sb_handle, 100,
-	    acpi_wake_prep, NULL, &stype, NULL);
+	    acpi_wake_prep, NULL, &ctx, NULL);
     return (0);
 }