diff --git a/src/dist/block_service/local/local_service.cpp b/src/dist/block_service/local/local_service.cpp
index 40e4a7a795..dbaec6dd28 100644
--- a/src/dist/block_service/local/local_service.cpp
+++ b/src/dist/block_service/local/local_service.cpp
@@ -413,7 +413,7 @@ dsn::task_ptr local_file_object::read(const read_request &req,
 
                 dinfo("read file(%s), size = %ld", file_name().c_str(), total_sz);
                 std::string buf;
-                buf.reserve(total_sz + 1);
+                buf.resize(total_sz + 1);
                 std::ifstream fin(file_name(), std::ifstream::in);
                 if (!fin.is_open()) {
                     resp.err = ERR_FS_INTERNAL;