diff --git a/lib/metricsql/parser.go b/lib/metricsql/parser.go
index 6feb3fe1c..10febd145 100644
--- a/lib/metricsql/parser.go
+++ b/lib/metricsql/parser.go
@@ -261,7 +261,7 @@ func (p *parser) parseWithArgExpr() (*withArgExpr, error) {
 		return nil, fmt.Errorf(`withArgExpr: unexpected token %q; want "ident"`, p.lex.Token)
 	}
 	wa.Name = p.lex.Token
-	if isAggrFunc(wa.Name) || isRollupFunc(wa.Name) || isTransformFunc(wa.Name) || isWith(wa.Name) {
+	if isAggrFunc(wa.Name) || IsRollupFunc(wa.Name) || IsTransformFunc(wa.Name) || isWith(wa.Name) {
 		return nil, fmt.Errorf(`withArgExpr: cannot use reserved name %q`, wa.Name)
 	}
 	if err := p.lex.Next(); err != nil {
diff --git a/lib/metricsql/rollup.go b/lib/metricsql/rollup.go
index aa3c63c1e..7406e1471 100644
--- a/lib/metricsql/rollup.go
+++ b/lib/metricsql/rollup.go
@@ -53,7 +53,8 @@ var rollupFuncs = map[string]bool{
 	"rollup_candlestick":  true,
 }
 
-func isRollupFunc(funcName string) bool {
-	funcName = strings.ToLower(funcName)
-	return rollupFuncs[funcName]
+// IsRollupFunc returns whether funcName is known rollup function.
+func IsRollupFunc(funcName string) bool {
+	s := strings.ToLower(funcName)
+	return rollupFuncs[s]
 }
diff --git a/lib/metricsql/transform.go b/lib/metricsql/transform.go
index 74f840f7e..16094dfdd 100644
--- a/lib/metricsql/transform.go
+++ b/lib/metricsql/transform.go
@@ -75,7 +75,9 @@ var transformFuncs = map[string]bool{
 	"histogram_share":    true,
 }
 
-func isTransformFunc(s string) bool {
-	s = strings.ToLower(s)
+// IsTransformFunc returns whether funcName is known transform function.
+func IsTransformFunc(funcName string) bool {
+	s := strings.ToLower(funcName)
 	return transformFuncs[s]
+
 }