diff --git a/dap_server_http_db_auth_tool.c b/dap_server_http_db_auth_tool.c
index b9d09129bef18cb0cf6593d86d685ed4e09061a5..904242b6e8d5fd24ad9c76a346192b1c2c36ad12 100644
--- a/dap_server_http_db_auth_tool.c
+++ b/dap_server_http_db_auth_tool.c
@@ -57,7 +57,7 @@ int main(int argc, const char * argv[])
 #elif _WIN32
     dap_sprintf(s_sys_dir_path, "%s/%s", regGetUsrPath(), dap_get_appname() );
 #endif
-    g_sys_dir_path_len = strlen(g_sys_dir_path);
+    size_t g_sys_dir_path_len = strlen(g_sys_dir_path);
 
     char * l_app_title = dap_strdup_printf("%s console interface",dap_get_appname());