diff --git a/substrate/frame/referenda/src/benchmarking.rs b/substrate/frame/referenda/src/benchmarking.rs
index 9abd3768f7..dfca7cdf46 100644
--- a/substrate/frame/referenda/src/benchmarking.rs
+++ b/substrate/frame/referenda/src/benchmarking.rs
@@ -101,8 +101,16 @@ fn info<T: Config>(index: ReferendumIndex) -> &'static TrackInfoOf<T> {
 }
 
 fn make_passing_after<T: Config>(index: ReferendumIndex, period_portion: Perbill) {
-	let support = info::<T>(index).min_support.threshold(period_portion);
-	let approval = info::<T>(index).min_approval.threshold(period_portion);
+	// We add an extra 1 percent to handle any perbill rounding errors which may cause
+	// a proposal to not actually pass.
+	let support = info::<T>(index)
+		.min_support
+		.threshold(period_portion)
+		.saturating_add(Perbill::from_percent(1));
+	let approval = info::<T>(index)
+		.min_approval
+		.threshold(period_portion)
+		.saturating_add(Perbill::from_percent(1));
 	Referenda::<T>::access_poll(index, |status| {
 		if let PollStatus::Ongoing(tally, class) = status {
 			*tally = T::Tally::from_requirements(support, approval, class);
diff --git a/substrate/frame/referenda/src/lib.rs b/substrate/frame/referenda/src/lib.rs
index 15c5562d64..e9e14e1d4a 100644
--- a/substrate/frame/referenda/src/lib.rs
+++ b/substrate/frame/referenda/src/lib.rs
@@ -699,7 +699,8 @@ impl<T: Config<I>, I: 'static> Pallet<T, I> {
 		when: T::BlockNumber,
 	) -> Option<(T::BlockNumber, ScheduleAddressOf<T, I>)> {
 		let alarm_interval = T::AlarmInterval::get().max(One::one());
-		let when = (when + alarm_interval - One::one()) / alarm_interval * alarm_interval;
+		let when = when.saturating_add(alarm_interval).saturating_sub(One::one()) /
+			(alarm_interval.saturating_mul(alarm_interval)).max(One::one());
 		let maybe_result = T::Scheduler::schedule(
 			DispatchTime::At(when),
 			None,
@@ -752,7 +753,8 @@ impl<T: Config<I>, I: 'static> Pallet<T, I> {
 			None
 		};
 		let deciding_status = DecidingStatus { since: now, confirming };
-		let alarm = Self::decision_time(&deciding_status, &status.tally, status.track, track);
+		let alarm = Self::decision_time(&deciding_status, &status.tally, status.track, track)
+			.max(now.saturating_add(One::one()));
 		status.deciding = Some(deciding_status);
 		let branch =
 			if is_passing { BeginDecidingBranch::Passing } else { BeginDecidingBranch::Failing };