diff --git a/luprex/core/cpp/streambuffer.cpp b/luprex/core/cpp/streambuffer.cpp
index 30911718..e0f4f360 100644
--- a/luprex/core/cpp/streambuffer.cpp
+++ b/luprex/core/cpp/streambuffer.cpp
@@ -455,7 +455,8 @@ util::HashValue StreamBuffer::hash() const {
 
 int StreamBuffer::lua_writer(lua_State *L, const void* p, size_t sz, void* ud) {
     StreamBuffer *sb = (StreamBuffer *)ud;
-    sb->write_bytes((const char *)p, sz);
+    memcpy(sb->make_space(sz), p, sz);
+    sb->write_cursor_ += sz;
     return 0;
 }