diff --git a/app/vmselect/promql/rollup.go b/app/vmselect/promql/rollup.go
index d6351e523..6d612fee9 100644
--- a/app/vmselect/promql/rollup.go
+++ b/app/vmselect/promql/rollup.go
@@ -474,6 +474,11 @@ func (rc *rollupConfig) doInternal(dstValues []float64, tsm *timeseriesMap, valu
 	window := rc.Window
 	if window <= 0 {
 		window = rc.Step
+		if rc.LookbackDelta > 0 && window > rc.LookbackDelta {
+			// Implicitly set window exceeds -search.maxStalenessInterval, so limit it to -search.maxStalenessInterval
+			// according to https://github.com/VictoriaMetrics/VictoriaMetrics/issues/784
+			window = rc.LookbackDelta
+		}
 	}
 	if rc.MayAdjustWindow && window < maxPrevInterval {
 		window = maxPrevInterval
diff --git a/app/vmselect/promql/rollup_test.go b/app/vmselect/promql/rollup_test.go
index c75626f45..d698d8c8e 100644
--- a/app/vmselect/promql/rollup_test.go
+++ b/app/vmselect/promql/rollup_test.go
@@ -645,7 +645,7 @@ func TestRollupFuncsLookbackDelta(t *testing.T) {
 		}
 		rc.Timestamps = getTimestamps(rc.Start, rc.End, rc.Step)
 		values := rc.Do(nil, testValues, testTimestamps)
-		valuesExpected := []float64{99, nan, 44, nan, 32, 34, nan}
+		valuesExpected := []float64{12, nan, nan, nan, 34, 34, nan}
 		timestampsExpected := []int64{80, 90, 100, 110, 120, 130, 140}
 		testRowsEqual(t, values, rc.Timestamps, valuesExpected, timestampsExpected)
 	})