diff --git a/sys/dev/acpica/acpi_apei.c b/sys/dev/acpica/acpi_apei.c
index 6a3d9d10edd4..3bab46b23978 100644
--- a/sys/dev/acpica/acpi_apei.c
+++ b/sys/dev/acpica/acpi_apei.c
@@ -665,6 +665,7 @@ apei_attach(device_t dev)
 	struct acpi_softc *acpi_sc;
 	struct apei_pges *pges;
 	struct apei_ge *ge;
+	struct resource *ack;
 	ACPI_STATUS status;
 	int rid;
 
@@ -698,6 +699,7 @@ apei_attach(device_t dev)
 	AcpiPutTable((ACPI_TABLE_HEADER *)sc->hest);
 
 	rid = 0;
+	ack = NULL;
 	TAILQ_FOREACH(ge, &sc->ges, link) {
 		ge->res_rid = rid++;
 		acpi_bus_alloc_gas(dev, &ge->res_type, &ge->res_rid,
@@ -709,11 +711,19 @@ apei_attach(device_t dev)
 			device_printf(dev, "Can't allocate status resource.\n");
 		}
 		if (ge->v1.Header.Type == ACPI_HEST_TYPE_GENERIC_ERROR_V2) {
-			ge->res2_rid = rid++;
-			acpi_bus_alloc_gas(dev, &ge->res2_type, &ge->res2_rid,
-			    &ge->v2.ReadAckRegister, &ge->res2, 0);
-			if (ge->res2 == NULL)
-				device_printf(dev, "Can't allocate ack resource.\n");
+			if (ack != NULL && rman_get_start(ack) ==
+			    ge->v2.ReadAckRegister.Address) {
+				ge->res2_rid = -1;
+				ge->res2 = ack;
+			} else {
+				ge->res2_rid = rid++;
+				acpi_bus_alloc_gas(dev, &ge->res2_type, &ge->res2_rid,
+				    &ge->v2.ReadAckRegister, &ge->res2, 0);
+				if (ge->res2 == NULL)
+					device_printf(dev, "Can't allocate ack resource.\n");
+				else if (ack == NULL)
+					ack = ge->res2;
+			}
 		}
 		if (ge->v1.Notify.Type == ACPI_HEST_NOTIFY_POLLED) {
 			pges = &sc->pges[PGE_ID(ge)];
@@ -770,7 +780,7 @@ apei_detach(device_t dev)
 			bus_release_resource(dev, ge->res_type,
 			    ge->res_rid, ge->res);
 		}
-		if (ge->res2) {
+		if (ge->res2 != NULL && ge->res2_rid >= 0) {
 			bus_release_resource(dev, ge->res2_type,
 			    ge->res2_rid, ge->res2);
 		}