diff --git a/src/stratifier.c b/src/stratifier.c
index 63d4cb07..a454581c 100644
--- a/src/stratifier.c
+++ b/src/stratifier.c
@@ -1735,7 +1735,9 @@ static void add_submit(ckpool_t *ckp, stratum_instance_t *client, int diff, bool
 	if (drr > 0.15 && drr < 0.4)
 		return;
 
-	optimal = round(dsps * 3.33);
+	/* Round away from zero to avoid bouncing around diffs at the lower
+	 * end of the scale. */
+	optimal = lround(dsps * 3.33);
 	/* Clamp to mindiff ~ network_diff */
 	if (optimal < ckp->mindiff)
 		optimal = ckp->mindiff;