diff --git a/src/print_json.cpp b/src/print_json.cpp
index f84f945..bf8366d 100644
--- a/src/print_json.cpp
+++ b/src/print_json.cpp
@@ -2,7 +2,7 @@
 #include "batched_print.hpp"
 #include "jsonutils.hpp"
 
-void print_json_inner(Builder builder, const unsigned flags, growing_string &indent);
+void print_json_inner(Builder& builder, const unsigned flags, growing_string &indent);
 
 void print_vector(Vector &vector_holder, const unsigned flags, growing_string &indent)
 {
@@ -80,7 +80,7 @@ void print_map(Map &map_holder, const unsigned flags, growing_string &indent)
     batched_print("}");
 }
 
-void print_json_inner(Builder builder, const unsigned flags, growing_string &indent)
+void print_json_inner(Builder& builder, const unsigned flags, growing_string &indent)
 {
     if (std::holds_alternative<string_variant>(builder))
     {
@@ -102,7 +102,7 @@ void print_json_inner(Builder builder, const unsigned flags, growing_string &ind
     }
 }
 
-void print_json(Builder builder, const unsigned flags)
+void print_json(Builder& builder, const unsigned flags)
 {
     growing_string indent;
     batched_out.reserve_extra(1000000);
diff --git a/src/print_json.hpp b/src/print_json.hpp
index ed5a6d5..9b1bee8 100644
--- a/src/print_json.hpp
+++ b/src/print_json.hpp
@@ -1,4 +1,4 @@
 #pragma once
 #include "builder.hpp"
 
-void print_json(Builder builder, const unsigned flags);
+void print_json(Builder& builder, const unsigned flags);