diff --git a/tsdb/errors/errors.go b/tsdb/errors/errors.go
index 21449e8950..6a8e72f049 100644
--- a/tsdb/errors/errors.go
+++ b/tsdb/errors/errors.go
@@ -38,7 +38,8 @@ func (es *multiError) Add(errs ...error) {
 		if err == nil {
 			continue
 		}
-		if merr, ok := err.(nonNilMultiError); ok {
+		var merr nonNilMultiError
+		if errors.As(err, &merr) {
 			*es = append(*es, merr.errs...)
 			continue
 		}