diff --git a/drivers/mailbox/mailbox-th1520.c b/drivers/mailbox/mailbox-th1520.c
index e16e7c85ee3c..a6b2aa9ae952 100644
--- a/drivers/mailbox/mailbox-th1520.c
+++ b/drivers/mailbox/mailbox-th1520.c
@@ -41,7 +41,7 @@
 #ifdef CONFIG_PM_SLEEP
 /* store MBOX context across system-wide suspend/resume transitions */
 struct th1520_mbox_context {
-	u32 intr_mask[TH_1520_MBOX_CHANS - 1];
+	u32 intr_mask[TH_1520_MBOX_CHANS];
 };
 #endif