diff --git a/src/support/lockedpool.cpp b/src/support/lockedpool.cpp
index 319a04984..52ee13385 100644
--- a/src/support/lockedpool.cpp
+++ b/src/support/lockedpool.cpp
@@ -27,6 +27,10 @@
 #endif
 
 #include <algorithm>
+#ifdef ARENA_DEBUG
+#include <iomanip>
+#include <iostream>
+#endif
 
 LockedPoolManager* LockedPoolManager::_instance = NULL;
 std::once_flag LockedPoolManager::init_flag;
@@ -153,7 +157,7 @@ void Arena::walk() const
         printchunk(chunk.first, chunk.second, true);
     std::cout << std::endl;
     for (const auto& chunk: chunks_free)
-        printchunk(chunk.first, chunk.second, false);
+        printchunk(chunk.first, chunk.second->first, false);
     std::cout << std::endl;
 }
 #endif