diff --git a/src/filter.c b/src/filter.c
index 7e935bff..dc299286 100644
--- a/src/filter.c
+++ b/src/filter.c
@@ -138,9 +138,10 @@ static double
 calculate_tracker_velocity(struct pointer_tracker *tracker, uint64_t time)
 {
 	double distance;
+	double tdelta = time - tracker->time + 1;
 
 	distance = hypot(tracker->delta.x, tracker->delta.y);
-	return distance / (double)(time - tracker->time); /* units/ms */
+	return distance / tdelta; /* units/ms */
 }
 
 static double