diff --git a/sys/arch/arm/cortex/gtmr.c b/sys/arch/arm/cortex/gtmr.c
index ceff19c..090d40b 100644
--- a/sys/arch/arm/cortex/gtmr.c
+++ b/sys/arch/arm/cortex/gtmr.c
@@ -129,12 +129,14 @@ gtmr_attach(device_t parent, device_t self, void *aux)
 	evcnt_attach_dynamic(&sc->sc_ev_missing_ticks, EVCNT_TYPE_MISC, NULL,
 	    device_xname(self), "missing interrupts");
 
-	sc->sc_global_ih = intr_establish(mpcaa->mpcaa_irq, IPL_CLOCK,
-	    IST_LEVEL | IST_MPSAFE, gtmr_intr, NULL);
-	if (sc->sc_global_ih == NULL)
-		panic("%s: unable to register timer interrupt", __func__);
-	aprint_normal_dev(self, "interrupting on irq %d\n",
-	    mpcaa->mpcaa_irq);
+	if (mpcaa->mpcaa_irq != -1) {
+		sc->sc_global_ih = intr_establish(mpcaa->mpcaa_irq, IPL_CLOCK,
+		    IST_LEVEL | IST_MPSAFE, gtmr_intr, NULL);
+		if (sc->sc_global_ih == NULL)
+			panic("%s: unable to register timer interrupt", __func__);
+		aprint_normal_dev(self, "interrupting on irq %d\n",
+		    mpcaa->mpcaa_irq);
+	}
 
 	const uint32_t cnt_frq = armreg_cnt_frq_read();
 	if (cnt_frq == 0) {
diff --git a/sys/arch/arm/fdt/gtmr_fdt.c b/sys/arch/arm/fdt/gtmr_fdt.c
index 2032bea..e06a827 100644
--- a/sys/arch/arm/fdt/gtmr_fdt.c
+++ b/sys/arch/arm/fdt/gtmr_fdt.c
@@ -72,8 +72,19 @@ gtmr_fdt_attach(device_t parent, device_t self, void *aux)
 
 	struct mpcore_attach_args mpcaa = {
 		.mpcaa_name = "armgtmr",
-		.mpcaa_irq = IRQ_GTMR_PPI_VTIMER
+		.mpcaa_irq = -1		/* setup handler locally */
 	};
+	struct fdt_attach_args * const faa = aux;
+	const int phandle = faa->faa_phandle;
+
+#define GTMR_VTIMER 2
+
+	void *ih = fdtbus_intr_establish(phandle, GTMR_VTIMER, IPL_SERIAL, FDT_INTR_MPSAFE,
+	    gtmr_intr, NULL);
+	if (ih == NULL) {
+		aprint_error_dev(self, "couldn't install interrupt handler\n");
+		return;
+	}
 
 	config_found(self, &mpcaa, NULL);