diff --git a/storage/remote/queue_manager.go b/storage/remote/queue_manager.go
index d7981a0936..32a4aba4ae 100644
--- a/storage/remote/queue_manager.go
+++ b/storage/remote/queue_manager.go
@@ -859,11 +859,13 @@ func (t *QueueManager) calculateDesiredShards() int {
 	)
 	level.Debug(t.logger).Log("msg", "QueueManager.updateShardsLoop",
 		"lowerBound", lowerBound, "desiredShards", desiredShards, "upperBound", upperBound)
+
+	desiredShards = math.Ceil(desiredShards) // Round up to be on the safe side.
 	if lowerBound <= desiredShards && desiredShards <= upperBound {
 		return t.numShards
 	}
 
-	numShards := int(math.Ceil(desiredShards))
+	numShards := int(desiredShards)
 	// Do not downshard if we are more than ten seconds back.
 	if numShards < t.numShards && delay > 10.0 {
 		level.Debug(t.logger).Log("msg", "Not downsharding due to being too far behind")
diff --git a/storage/remote/queue_manager_test.go b/storage/remote/queue_manager_test.go
index 56498a0f08..a2d63b0bcb 100644
--- a/storage/remote/queue_manager_test.go
+++ b/storage/remote/queue_manager_test.go
@@ -1025,7 +1025,7 @@ func TestCalculateDesiredShardsDetail(t *testing.T) {
 			dataIn:          10,
 			dataOut:         10,
 			dataOutDuration: 1.2,
-			expectedShards:  1, // no reaction - less than 30% change
+			expectedShards:  2, // 1.2 is rounded up to 2.
 		},
 		{
 			name:            "bigger slowdown",
@@ -1033,7 +1033,7 @@ func TestCalculateDesiredShardsDetail(t *testing.T) {
 			dataIn:          10,
 			dataOut:         10,
 			dataOutDuration: 1.4,
-			expectedShards:  2, // now it shards up
+			expectedShards:  2,
 		},
 		{
 			name:            "speed up",