diff --git a/tests/test_daily_logger.cpp b/tests/test_daily_logger.cpp
index fe4783cb..7585257e 100644
--- a/tests/test_daily_logger.cpp
+++ b/tests/test_daily_logger.cpp
@@ -46,12 +46,10 @@ TEST_CASE("daily_logger with dateonly calculator", "[daily_logger]") {
 
 struct custom_daily_file_name_calculator {
     static spdlog::filename_t calc_filename(const spdlog::filename_t &basename, const tm &now_tm) {
-        filename_memory_buf_t w;
-        spdlog::fmt_lib::format_to(std::back_inserter(w), SPDLOG_FILENAME_T("{}{:04d}{:02d}{:02d}"),
+        
+        return spdlog::fmt_lib::format(SPDLOG_FILENAME_T("{}{:04d}{:02d}{:02d}"),
                                    basename, now_tm.tm_year + 1900, now_tm.tm_mon + 1,
-                                   now_tm.tm_mday);
-
-        return SPDLOG_BUF_TO_STRING(w);
+                                   now_tm.tm_mday);        
     }
 };