diff --git a/drivers/watchdog/rzg2l_wdt.c b/drivers/watchdog/rzg2l_wdt.c
index 6b426df34fd6fd..96f2a018ab6261 100644
--- a/drivers/watchdog/rzg2l_wdt.c
+++ b/drivers/watchdog/rzg2l_wdt.c
@@ -53,7 +53,7 @@ static void rzg2l_wdt_wait_delay(struct rzg2l_wdt_priv *priv)
 
 static u32 rzg2l_wdt_get_cycle_usec(unsigned long cycle, u32 wdttime)
 {
-	u64 timer_cycle_us = 1024 * 1024 * (wdttime + 1) * MICRO;
+	u64 timer_cycle_us = 1024 * 1024ULL * (wdttime + 1) * MICRO;
 
 	return div64_ul(timer_cycle_us, cycle);
 }