diff --git a/promql/parser/ast.go b/promql/parser/ast.go
index 3c5858ce40..64b4a2ec6a 100644
--- a/promql/parser/ast.go
+++ b/promql/parser/ast.go
@@ -198,11 +198,12 @@ type VectorSelector struct {
 	// Offset is the offset used during the query execution
 	// which is calculated using the original offset, at modifier time,
 	// eval time, and subquery offsets in the AST tree.
+	SkipHistogramBuckets bool // Set when decoding native histogram buckets is not needed for query evaluation.
 	Offset               time.Duration
 	Timestamp            *int64
-	SkipHistogramBuckets bool     // Set when decoding native histogram buckets is not needed for query evaluation.
 	StartOrEnd           ItemType // Set when @ is used with start() or end()
 	LabelMatchers        []*labels.Matcher
+	LookbackDelta        time.Duration
 
 	// The unexpanded seriesSet populated at query preparation time.
 	UnexpandedSeriesSet storage.SeriesSet
@@ -215,6 +216,14 @@ type VectorSelector struct {
 	PosRange posrange.PositionRange
 }
 
+func (m *VectorSelector) GetLookbackDelta(d time.Duration) time.Duration {
+	if m.LookbackDelta > 0 {
+		return m.LookbackDelta
+	}
+
+	return d
+}
+
 // TestStmt is an internal helper statement that allows execution
 // of an arbitrary function during handling. It is used to test the Engine.
 type TestStmt func(context.Context) error