diff --git a/src/unit_map.hpp b/src/unit_map.hpp
index 7e63cf9360b..704f6438887 100644
--- a/src/unit_map.hpp
+++ b/src/unit_map.hpp
@@ -24,7 +24,6 @@
 
 #include <cassert>
 #include <list>
-#include <iostream>
 #include <boost/unordered_map.hpp>
 
 class unit;
@@ -191,11 +190,14 @@ public:
 			return  i_->unit; }
 		reference operator*() const {
 			tank_->self_check();
+#if 0
+			// debug!
 			if(!valid()){
 				if(!tank_){std::cerr<<"tank is NULL"<<"\n";}
 				if(i_==the_end()){std::cerr<<"i_ is the end"<<"\n";}
 				if(i_->unit==NULL){std::cerr<<"i_ unit is NULL with uid="<<i_->deleted_uid<<"\n";}
 			}
+#endif
 			assert(valid());
 			return *i_->unit; }