diff --git a/src/cs_util.cc b/src/cs_util.cc
index 138b680..637d1dc 100644
--- a/src/cs_util.cc
+++ b/src/cs_util.cc
@@ -546,7 +546,7 @@ OSTD_EXPORT void list_find_item(cs_list_parse_state &ps) {
 OSTD_EXPORT cs_strref value_list_concat(
     cs_state &cs, cs_value_r vals, ostd::string_range sep
 ) {
-    auto app = ostd::appender<cs_string>();
+    auto app = ostd::appender<cs_charbuf>(cs);
     for (std::size_t i = 0; i < vals.size(); ++i) {
         switch (vals[i].get_type()) {
             case cs_value_type::INT:
@@ -564,7 +564,7 @@ OSTD_EXPORT cs_strref value_list_concat(
         }
         ostd::range_put_all(app, sep);
     }
-    return cs_strref{cs, ostd::iter(app.get())};
+    return cs_strref{cs, app.get().str()};
 }
 
 } /* namespace cscript */
diff --git a/src/cs_util.hh b/src/cs_util.hh
index 719b2cb..fcabc69 100644
--- a/src/cs_util.hh
+++ b/src/cs_util.hh
@@ -15,8 +15,6 @@ using cs_map = std::unordered_map<K, V>;
 template<typename T>
 using cs_vector = std::vector<T>;
 
-using cs_string = std::string;
-
 cs_int cs_parse_int(
     ostd::string_range input, ostd::string_range *end = nullptr
 );
diff --git a/src/cubescript.cc b/src/cubescript.cc
index 96948fb..a6c6372 100644
--- a/src/cubescript.cc
+++ b/src/cubescript.cc
@@ -1036,9 +1036,9 @@ void cs_init_lib_base(cs_state &gcs) {
         } catch (cs_error const &e) {
             result.set_str(e.what());
             if (e.get_stack().get()) {
-                auto app = ostd::appender<cs_string>();
+                auto app = ostd::appender<cs_charbuf>(cs);
                 cscript::util::print_stack(app, e.get_stack());
-                tback.set_str(app.get());
+                tback.set_str(app.get().str());
             }
             rc = false;
         }