diff --git a/NPLib/Core/NPOptionManager.cxx b/NPLib/Core/NPOptionManager.cxx
index 0a272122be570db2add232afc7a7d35d1ff73e62..df51eca26f049d8e06aa7c72d8b0eb23981dc8e7 100644
--- a/NPLib/Core/NPOptionManager.cxx
+++ b/NPLib/Core/NPOptionManager.cxx
@@ -215,6 +215,9 @@ NPOptionManager::NPOptionManager(int argc, char** argv){
 }
 ////////////////////////////////////////////////////////////////////////////////
 NPOptionManager::NPOptionManager(std::string arg){  
+  // add dummy string in front of arg string
+  arg.insert(0, "ignore ");
+
   std::vector<char *> args;
   std::stringstream iss(arg);