Index: head/sys/dev/acpi_support/acpi_ibm.c
===================================================================
--- head/sys/dev/acpi_support/acpi_ibm.c
+++ head/sys/dev/acpi_support/acpi_ibm.c
@@ -485,6 +485,9 @@
 	/* Enable per-model events. */
 	maker = kern_getenv("smbios.system.maker");
 	product = kern_getenv("smbios.system.product");
+	if (maker != NULL && product != NULL)
+		goto nosmbios;
+
 	for (i = 0; i < nitems(acpi_ibm_models); i++) {
 		if (strcmp(maker, acpi_ibm_models[i].maker) == 0 &&
 		    strcmp(product, acpi_ibm_models[i].product) == 0) {
@@ -494,6 +497,8 @@
 			ACPI_SERIAL_END(ibm);
 		}
 	}
+
+nosmbios:
 	freeenv(maker);
 	freeenv(product);