diff --git a/promql/durations.go b/promql/durations.go
index 20fa095d53..6249faa539 100644
--- a/promql/durations.go
+++ b/promql/durations.go
@@ -21,12 +21,20 @@ import (
 	"github.com/prometheus/prometheus/promql/parser"
 )
 
-// durationVisitor is a visitor that visits a duration expression and calculates the duration.
-type durationVisitor struct {
+// DurationVisitor is a visitor that visits a duration expression and calculates the duration.
+type DurationVisitor struct {
 	step time.Duration
 }
 
-func (v *durationVisitor) Visit(node parser.Node, _ []parser.Node) (parser.Visitor, error) {
+// NewDurationVisitor creates a visitor to Walk and evaluate duration
+// expressions in a parsed query.
+func NewDurationVisitor(step time.Duration) *DurationVisitor {
+	return &DurationVisitor{
+		step: step,
+	}
+}
+
+func (v *DurationVisitor) Visit(node parser.Node, _ []parser.Node) (parser.Visitor, error) {
 	switch n := node.(type) {
 	case *parser.VectorSelector:
 		if n.OriginalOffsetExpr != nil {
@@ -71,7 +79,7 @@ func (v *durationVisitor) Visit(node parser.Node, _ []parser.Node) (parser.Visit
 }
 
 // calculateDuration computes the duration from a duration expression.
-func (v *durationVisitor) calculateDuration(expr parser.Expr, allowedNegative bool) (time.Duration, error) {
+func (v *DurationVisitor) calculateDuration(expr parser.Expr, allowedNegative bool) (time.Duration, error) {
 	duration, err := v.evaluateDurationExpr(expr)
 	if err != nil {
 		return 0, err
@@ -86,7 +94,7 @@ func (v *durationVisitor) calculateDuration(expr parser.Expr, allowedNegative bo
 }
 
 // evaluateDurationExpr recursively evaluates a duration expression to a float64 value.
-func (v *durationVisitor) evaluateDurationExpr(expr parser.Expr) (float64, error) {
+func (v *DurationVisitor) evaluateDurationExpr(expr parser.Expr) (float64, error) {
 	switch n := expr.(type) {
 	case *parser.NumberLiteral:
 		return n.Val, nil
diff --git a/promql/durations_test.go b/promql/durations_test.go
index 18592a0d0a..bee3cd7800 100644
--- a/promql/durations_test.go
+++ b/promql/durations_test.go
@@ -41,7 +41,7 @@ func TestDurationVisitor(t *testing.T) {
 	expr, err := parser.ParseExpr(complexExpr)
 	require.NoError(t, err)
 
-	err = parser.Walk(&durationVisitor{}, expr, nil)
+	err = parser.Walk(NewDurationVisitor(0), expr, nil)
 	require.NoError(t, err)
 
 	// Verify different parts of the expression have correct durations.
@@ -243,7 +243,7 @@ func TestCalculateDuration(t *testing.T) {
 
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
-			v := &durationVisitor{step: 1 * time.Second}
+			v := NewDurationVisitor(1 * time.Second)
 			result, err := v.calculateDuration(tt.expr, tt.allowedNegative)
 			if tt.errorMessage != "" {
 				require.Error(t, err)
diff --git a/promql/engine.go b/promql/engine.go
index f5ee591d3b..3dc9ffb920 100644
--- a/promql/engine.go
+++ b/promql/engine.go
@@ -3734,7 +3734,7 @@ func unwrapStepInvariantExpr(e parser.Expr) parser.Expr {
 func PreprocessExpr(expr parser.Expr, start, end time.Time, step time.Duration) (parser.Expr, error) {
 	detectHistogramStatsDecoding(expr)
 
-	if err := parser.Walk(&durationVisitor{step: step}, expr, nil); err != nil {
+	if err := parser.Walk(NewDurationVisitor(step), expr, nil); err != nil {
 		return nil, err
 	}