diff --git a/arch/arm/boot/dts/dm816x.dtsi b/arch/arm/boot/dts/dm816x.dtsi
index 3c99cfa1a8761604a409b9d0525f143c494571b0..a7a34e47dadc6059447bc6fefada6bba33d14505 100644
--- a/arch/arm/boot/dts/dm816x.dtsi
+++ b/arch/arm/boot/dts/dm816x.dtsi
@@ -218,6 +218,7 @@
 			reg = <0x480c8000 0x2000>;
 			interrupts = <77>;
 			ti,hwmods = "mailbox";
+			#mbox-cells = <1>;
 			ti,mbox-num-users = <4>;
 			ti,mbox-num-fifos = <12>;
 			mbox_dsp: mbox_dsp {