diff --git a/lib/lrama/grammar/rule_builder.rb b/lib/lrama/grammar/rule_builder.rb
index c1e8091c..faa156f7 100644
--- a/lib/lrama/grammar/rule_builder.rb
+++ b/lib/lrama/grammar/rule_builder.rb
@@ -118,7 +118,7 @@ def process_rhs(parameterizing_rule_resolver)
               parameterizing_rule.rhs_list.each do |r|
                 rule_builder = RuleBuilder.new(@rule_counter, @midrule_action_counter, i, lhs_tag: token.lhs_tag, skip_preprocess_references: true)
                 rule_builder.lhs = new_token
-                r.symbols.map { |sym| rule_builder.add_rhs(binding.resolve_symbol(sym)) }
+                r.symbols.each { |sym| rule_builder.add_rhs(binding.resolve_symbol(sym)) }
                 rule_builder.line = line
                 rule_builder.user_code = r.user_code
                 rule_builder.precedence_sym = r.precedence_sym