diff --git a/sys/arm/arm/generic_timer.c b/sys/arm/arm/generic_timer.c
--- a/sys/arm/arm/generic_timer.c
+++ b/sys/arm/arm/generic_timer.c
@@ -574,15 +574,25 @@
 	return (0);
 }
 
+static device_method_t arm_tmr_methods[] = {
+	DEVMETHOD(device_attach,	arm_tmr_attach),
+
+	DEVMETHOD_END,
+};
+
+DEFINE_CLASS_0(generic_timer, arm_tmr_driver, arm_tmr_methods, 0);
+
 #ifdef FDT
 static device_method_t arm_tmr_fdt_methods[] = {
 	DEVMETHOD(device_probe,		arm_tmr_fdt_probe),
-	DEVMETHOD(device_attach,	arm_tmr_attach),
+
 	{ 0, 0 }
 };
 
-static DEFINE_CLASS_0(generic_timer, arm_tmr_fdt_driver, arm_tmr_fdt_methods,
-    sizeof(struct arm_tmr_softc));
+#define generic_timer_baseclasses generic_timer_fdt_baseclasses
+DEFINE_CLASS_1(generic_timer, arm_tmr_fdt_driver, arm_tmr_fdt_methods,
+    sizeof(struct arm_tmr_softc), arm_tmr_driver);
+#undef generic_timer_baseclasses
 
 EARLY_DRIVER_MODULE(timer, simplebus, arm_tmr_fdt_driver, 0, 0,
     BUS_PASS_TIMER + BUS_PASS_ORDER_MIDDLE);
@@ -594,12 +604,13 @@
 static device_method_t arm_tmr_acpi_methods[] = {
 	DEVMETHOD(device_identify,	arm_tmr_acpi_identify),
 	DEVMETHOD(device_probe,		arm_tmr_acpi_probe),
-	DEVMETHOD(device_attach,	arm_tmr_attach),
 	{ 0, 0 }
 };
 
-static DEFINE_CLASS_0(generic_timer, arm_tmr_acpi_driver, arm_tmr_acpi_methods,
-    sizeof(struct arm_tmr_softc));
+#define generic_timer_baseclasses generic_timer_acpi_baseclasses
+DEFINE_CLASS_1(generic_timer, arm_tmr_acpi_driver, arm_tmr_acpi_methods,
+    sizeof(struct arm_tmr_softc), arm_tmr_driver);
+#undef generic_timer_baseclasses
 
 EARLY_DRIVER_MODULE(timer, acpi, arm_tmr_acpi_driver, 0, 0,
     BUS_PASS_TIMER + BUS_PASS_ORDER_MIDDLE);