diff --git a/src/server/game/Maps/MapManager.cpp b/src/server/game/Maps/MapManager.cpp
index 75bd2f81f1b..2f5d5449a4b 100644
--- a/src/server/game/Maps/MapManager.cpp
+++ b/src/server/game/Maps/MapManager.cpp
@@ -35,7 +35,7 @@
 #include <boost/dynamic_bitset.hpp>
 
 MapManager::MapManager()
-    : _nextInstanceId(0), _scheduledScripts(0)
+    : _freeInstanceIds(std::make_unique<InstanceIds>()), _nextInstanceId(0), _scheduledScripts(0)
 {
     i_gridCleanUpDelay = sWorld->getIntConfig(CONFIG_INTERVAL_GRIDCLEAN);
     i_timer.SetInterval(sWorld->getIntConfig(CONFIG_INTERVAL_MAPUPDATE));