diff --git a/runtime/vam/op/exprswitch.go b/runtime/vam/op/exprswitch.go
index e4d55f459a..e9e0f3f7da 100644
--- a/runtime/vam/op/exprswitch.go
+++ b/runtime/vam/op/exprswitch.go
@@ -36,7 +36,7 @@ func (s *ExprSwitch) AddCase(val *super.Value) vector.Puller {
 }
 
 func (s *ExprSwitch) forward(vec vector.Any) bool {
-	clear(s.caseIndexes)
+	defer clear(s.caseIndexes)
 	exprVec := s.expr.Eval(vec)
 	for i := range exprVec.Len() {
 		s.builder.Truncate()