diff --git a/drivers/mfd/sm501.c b/drivers/mfd/sm501.c
index e0173bf4b0dc7e15c39fffb278dc100e29eb03b6..d217debf382eb502ada83c67205bcf84ab1f64f0 100644
--- a/drivers/mfd/sm501.c
+++ b/drivers/mfd/sm501.c
@@ -1142,8 +1142,7 @@ static int sm501_register_gpio_i2c_instance(struct sm501_devdata *sm,
 		return -ENOMEM;
 
 	/* Create a gpiod lookup using gpiochip-local offsets */
-	lookup = devm_kzalloc(&pdev->dev,
-			      sizeof(*lookup) + 3 * sizeof(struct gpiod_lookup),
+	lookup = devm_kzalloc(&pdev->dev, struct_size(lookup, table, 3),
 			      GFP_KERNEL);
 	if (!lookup)
 		return -ENOMEM;