diff --git a/src/nav_module.cpp b/src/nav_module.cpp
index 85a049e35b4ff010b5f7a41d519b696a48f52a05..667e3e5fa339da423b7c9cd62e5d01d43325692b 100644
--- a/src/nav_module.cpp
+++ b/src/nav_module.cpp
@@ -860,11 +860,11 @@ bool CNavModule::set_parameter(const std::string &name_space,const std::string &
   std::string::size_type pos;
   std::string rem_name_space,current_name_space;
 
-  ROS_DEBUG("%s", name_space);
+  ROS_DEBUG("%s", name_space.c_str());
   if((pos=name_space.find("move_base"))!=std::string::npos)// string exists
   {
     rem_name_space=name_space.substr(pos);
-    ROS_DEBUG("%s", rem_name_space);
+    ROS_DEBUG("%s", rem_name_space.c_str());
     if((pos=rem_name_space.find("/"))!=std::string::npos)// there exist some sub name_space
     {
       current_name_space=rem_name_space.substr(0,pos);