diff --git a/core/types/transaction.go b/core/types/transaction.go
index e104f1bb1c..7870746d54 100644
--- a/core/types/transaction.go
+++ b/core/types/transaction.go
@@ -489,7 +489,7 @@ func (tx *Transaction) Authorities() []common.Address {
 	if !ok {
 		return nil
 	}
-	auths := make([]common.Address, len(setcodetx.AuthList))
+	auths := make([]common.Address, 0, len(setcodetx.AuthList))
 	for _, auth := range setcodetx.AuthList {
 		if addr, err := auth.Authority(); err == nil {
 			auths = append(auths, addr)