diff --git a/include/cubescript/cubescript.hh b/include/cubescript/cubescript.hh
index aa80f015..691b83dc 100644
--- a/include/cubescript/cubescript.hh
+++ b/include/cubescript/cubescript.hh
@@ -424,7 +424,7 @@ struct OSTD_EXPORT CsState {
 
     template<typename F>
     bool pcall(
-        F func, ostd::String *error = nullptr,
+        F func, ostd::ConstCharRange *error = nullptr,
         CsStackState *stack = nullptr
     ) {
         return ipcall([](void *data) {
@@ -436,9 +436,15 @@ struct OSTD_EXPORT CsState {
 
     template<typename ...A>
     void error(ostd::ConstCharRange msg, A &&...args) {
-        auto app = ostd::appender<CsString>();
-        ostd::format(app, msg, ostd::forward<A>(args)...);
-        error(app.get());
+        char fbuf[512];
+        auto ret = ostd::format(
+            ostd::CharRange(fbuf, sizeof(fbuf)), msg, ostd::forward<A>(args)...
+        );
+        if ((ret < 0) || (ostd::Size(ret) > sizeof(fbuf))) {
+            error(msg);
+        } else {
+            error(ostd::CharRange(fbuf, ret));
+        }
     }
 
     void clear_override(CsIdent &id);
@@ -579,10 +585,11 @@ struct OSTD_EXPORT CsState {
 private:
     CsIdent *add_ident(CsIdent *id);
     bool ipcall(
-        void (*f)(void *data), ostd::String *error,
+        void (*f)(void *data), ostd::ConstCharRange *error,
         CsStackState *stack, void *data
     );
 
+    char p_errbuf[512];
     CsHookCb p_callhook;
     CsPanicCb p_panicfunc;
     CsStream *p_out, *p_err;
diff --git a/src/cs_vm.hh b/src/cs_vm.hh
index 80bd9c33..bda03000 100644
--- a/src/cs_vm.hh
+++ b/src/cs_vm.hh
@@ -99,15 +99,15 @@ constexpr ostd::Size CsTypeStorageSize =
     (sizeof(T) - 1) / sizeof(ostd::Uint32) + 1;
 
 struct CsErrorException {
-    CsString errmsg;
+    ostd::ConstCharRange errmsg;
     CsStackState stack;
     CsErrorException() = delete;
     CsErrorException(CsErrorException const &) = delete;
     CsErrorException(CsErrorException &&v):
-        errmsg(ostd::move(v.errmsg)), stack(ostd::move(v.stack))
+        errmsg(v.errmsg), stack(ostd::move(v.stack))
     {}
-    CsErrorException(CsString &&v, CsStackState &&st):
-        errmsg(ostd::move(v)), stack(ostd::move(st))
+    CsErrorException(ostd::ConstCharRange v, CsStackState &&st):
+        errmsg(v), stack(ostd::move(st))
     {}
 };
 
diff --git a/src/cubescript.cc b/src/cubescript.cc
index 78fc522d..4bed52fe 100644
--- a/src/cubescript.cc
+++ b/src/cubescript.cc
@@ -430,7 +430,7 @@ CsPanicCb &CsState::get_panic_func() {
 }
 
 bool CsState::ipcall(
-    void (*f)(void *data), ostd::String *error,
+    void (*f)(void *data), ostd::ConstCharRange *error,
     CsStackState *stack, void *data
 ) {
     ++protect;
@@ -439,7 +439,7 @@ bool CsState::ipcall(
     } catch (CsErrorException &v) {
         --protect;
         if (error) {
-            *error = ostd::move(v.errmsg);
+            *error = v.errmsg;
         }
         if (stack) {
             *stack = ostd::move(v.stack);
@@ -454,11 +454,16 @@ bool CsState::ipcall(
 }
 
 void CsState::error(ostd::ConstCharRange msg) {
+    if (msg.size() > sizeof(p_errbuf)) {
+        msg = msg.slice(0, sizeof(p_errbuf));
+    }
+    memcpy(p_errbuf, msg.data(), msg.size());
+    auto err = ostd::ConstCharRange(p_errbuf, msg.size());
     if (protect) {
-        throw CsErrorException(msg, cs_save_stack(*this));
+        throw CsErrorException(err, cs_save_stack(*this));
     } else {
         if (p_panicfunc) {
-            p_panicfunc(*this, msg, cs_save_stack(*this));
+            p_panicfunc(*this, err, cs_save_stack(*this));
         }
         exit(EXIT_FAILURE);
     }
@@ -1140,7 +1145,7 @@ void cs_init_lib_base(CsState &gcs) {
             ret.set_int(0);
             return;
         }
-        CsString errmsg;
+        ostd::ConstCharRange errmsg;
         CsValue result, tback;
         CsStackState stack;
         bool rc = cs.pcall([&cs, &args, &result]() {
@@ -1148,7 +1153,7 @@ void cs_init_lib_base(CsState &gcs) {
         }, &errmsg, &stack);
         ret.set_int(rc);
         if (!rc) {
-            result.set_str(ostd::move(errmsg));
+            result.set_str(errmsg);
             if (stack.get()) {
                 auto app = ostd::appender<CsString>();
                 cscript::util::print_stack(app, stack);
diff --git a/tools/repl.cc b/tools/repl.cc
index 0887d864..ca09c26e 100644
--- a/tools/repl.cc
+++ b/tools/repl.cc
@@ -194,7 +194,7 @@ static bool do_call(CsState &cs, ostd::ConstCharRange line, bool file = false) {
     CsValue ret;
     scs = &cs;
     signal(SIGINT, do_sigint);
-    ostd::String err;
+    ostd::ConstCharRange err;
     cscript::CsStackState st;
     auto tocall = [&]() {
         if (file) {