diff --git a/embassy-stm32/src/time_driver.rs b/embassy-stm32/src/time_driver.rs
index ab55cc08..8e84570a 100644
--- a/embassy-stm32/src/time_driver.rs
+++ b/embassy-stm32/src/time_driver.rs
@@ -296,7 +296,7 @@ impl Driver for RtcDriver {
         critical_section::with(|cs| {
             let r = T::regs_gp16();
 
-            let n = alarm.id() as _;
+            let n = alarm.id() as usize;
             let alarm = self.get_alarm(cs, alarm);
             alarm.timestamp.set(timestamp);