diff --git a/src/client/thingtypemanager.cpp b/src/client/thingtypemanager.cpp
index 8c7ed9e3..7b6968b4 100644
--- a/src/client/thingtypemanager.cpp
+++ b/src/client/thingtypemanager.cpp
@@ -199,11 +199,12 @@ void ThingTypeManager::loadOtb(const std::string& file)
             root->skip(128); // description
         }
 
+        BinaryTreeVec children = root->getChildren();
         m_reverseItemTypes.clear();
-        m_itemTypes.resize(root->getChildren().size() + 1, m_nullItemType);
-        m_reverseItemTypes.resize(root->getChildren().size() + 1, m_nullItemType);
+        m_itemTypes.resize(children.size() + 1, m_nullItemType);
+        m_reverseItemTypes.resize(children.size() + 1, m_nullItemType);
 
-        for(const BinaryTreePtr& node : root->getChildren()) {
+        for(const BinaryTreePtr& node : children) {
             ItemTypePtr itemType(new ItemType);
             itemType->unserialize(node);
             addItemType(itemType);