diff --git a/estimator/estimator.go b/estimator/estimator.go
index 44349c0..493f208 100644
--- a/estimator/estimator.go
+++ b/estimator/estimator.go
@@ -40,9 +40,8 @@ func (e *Estimator) swap(now uint64) {
 
 	var rate, packetRate uint32
 	if jiffies >= rtptime.JiffiesPerSec/1000 {
-		rate = uint32(uint64(bytes) * rtptime.JiffiesPerSec / jiffies)
-		packetRate =
-			uint32(uint64(packets) * rtptime.JiffiesPerSec / jiffies)
+		rate = uint32((uint64(bytes)*rtptime.JiffiesPerSec + jiffies/2) / jiffies)
+		packetRate = uint32((uint64(packets)*rtptime.JiffiesPerSec + jiffies/2) / jiffies)
 	}
 	atomic.StoreUint32(&e.rate, rate)
 	atomic.StoreUint32(&e.packetRate, packetRate)
diff --git a/estimator/estimator_test.go b/estimator/estimator_test.go
index 7376612..3c68ce2 100644
--- a/estimator/estimator_test.go
+++ b/estimator/estimator_test.go
@@ -2,13 +2,14 @@ package estimator
 
 import (
 	"testing"
+	"time"
 
 	"github.com/jech/galene/rtptime"
 )
 
 func TestEstimator(t *testing.T) {
 	now := rtptime.Jiffies()
-	e := New(rtptime.JiffiesPerSec)
+	e := New(time.Second)
 
 	e.estimate(now)
 	e.Accumulate(42)