diff --git a/drivers/bus/sunxi-rsb.c b/drivers/bus/sunxi-rsb.c
index b4f2c64ac181..daf0ea563e47 100644
--- a/drivers/bus/sunxi-rsb.c
+++ b/drivers/bus/sunxi-rsb.c
@@ -445,6 +445,9 @@ static int regmap_sunxi_rsb_reg_write(void *context, unsigned int reg,
 	struct sunxi_rsb_ctx *ctx = context;
 	struct sunxi_rsb_device *rdev = ctx->rdev;
 
+	if (reg > 0xff)
+		return -EINVAL;
+
 	return sunxi_rsb_write(rdev->rsb, rdev->rtaddr, reg, &val, ctx->size);
 }