Index: sys/dev/acpi_support/acpi_ibm.c
===================================================================
--- sys/dev/acpi_support/acpi_ibm.c
+++ sys/dev/acpi_support/acpi_ibm.c
@@ -485,13 +485,15 @@
 	/* Enable per-model events. */
 	maker = kern_getenv("smbios.system.maker");
 	product = kern_getenv("smbios.system.product");
-	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) {
-			ACPI_SERIAL_BEGIN(ibm);
-			acpi_ibm_sysctl_set(sc, ACPI_IBM_METHOD_EVENTMASK,
-			    acpi_ibm_models[i].eventmask);
-			ACPI_SERIAL_END(ibm);
+	if (maker != NULL && product != NULL) {
+		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) {
+				ACPI_SERIAL_BEGIN(ibm);
+				acpi_ibm_sysctl_set(sc, ACPI_IBM_METHOD_EVENTMASK,
+				    acpi_ibm_models[i].eventmask);
+				ACPI_SERIAL_END(ibm);
+			}
 		}
 	}
 	freeenv(maker);