diff --git a/libs/container/container.h b/libs/container/container.h
index 9e8c03f5..ab04b609 100644
--- a/libs/container/container.h
+++ b/libs/container/container.h
@@ -74,20 +74,20 @@ private:
 struct Compare{
 	using is_transparent = void;
 
-	bool operator()( const iterator& one, const iterator& other ) const {
+	bool operator()( const const_iterator& one, const const_iterator& other ) const {
 		return *one < *other;
 	}
-	bool operator()( const Value& va, const iterator& it ) const {
+	bool operator()( const Value& va, const const_iterator& it ) const {
 		return va < *it;
 	}
-	bool operator()( const iterator& it, const Value& va ) const {
+	bool operator()( const const_iterator& it, const Value& va ) const {
 		return *it < va;
 	}
 };
-std::set<iterator, Compare> m_set; // store sorted iterators for fast lookup
+std::set<const_iterator, Compare> m_set; // store sorted iterators for fast lookup
 void init_set(){ // only load set, when lookup is needed
 	if( m_set.empty() )
-		for( auto it = begin(); it != end(); ++it )
+		for( const_iterator it = begin(); it != end(); ++it )
 			m_set.emplace( it );
 }
 public:
@@ -154,14 +154,14 @@ iterator insert( const Value& value ){
 void erase( const Value& value ){
 	init_set();
 	const auto it = m_set.find( value );
-	ASSERT_MESSAGE( it != m_set.end(), "UnsortedSet::erase: not found" );
+	ASSERT_MESSAGE( it != m_set.cend(), "UnsortedSet::erase: not found" );
 	m_values.erase( *it );
 	m_set.erase( it );
 }
-iterator find( const Value& value ){
+const_iterator find( const Value& value ){
 	init_set();
 	const auto it = m_set.find( value );
-	return it == m_set.end()? m_values.end() : *it;
+	return it == m_set.cend()? end() : *it;
 }
 };
 
diff --git a/libs/selectionlib.h b/libs/selectionlib.h
index 022d62d7..2862bad7 100644
--- a/libs/selectionlib.h
+++ b/libs/selectionlib.h
@@ -121,6 +121,7 @@ typedef MemberCaller1<SelectableInstance, const Selectable&, &SelectableInstance
 #include <list>
 #include <set>
 
+/// It's illegal to modify inserted values directly!
 template<typename Selected>
 class SelectionList
 {
@@ -133,17 +134,17 @@ private:
 struct Compare{
 	using is_transparent = void;
 
-	bool operator()( const iterator& one, const iterator& other ) const {
+	bool operator()( const const_iterator& one, const const_iterator& other ) const {
 		return *one < *other;
 	}
-	bool operator()( const Selected* va, const iterator& it ) const {
+	bool operator()( const Selected* va, const const_iterator& it ) const {
 		return va < *it;
 	}
-	bool operator()( const iterator& it, const Selected* va ) const {
+	bool operator()( const const_iterator& it, const Selected* va ) const {
 		return *it < va;
 	}
 };
-std::multiset<iterator, Compare> m_set;
+std::multiset<const_iterator, Compare> m_set;
 public:
 
 SelectionList() = default;
@@ -181,8 +182,8 @@ void append( Selected& selected ){
 	m_set.emplace( --end() );
 }
 void erase( Selected& selected ){
-	auto it = m_set.find( &selected );
-	ASSERT_MESSAGE( it != m_set.end(), "selection-tracking error" );
+	const auto it = m_set.find( &selected );
+	ASSERT_MESSAGE( it != m_set.cend(), "selection-tracking error" );
 	m_selection.erase( *it );
 	m_set.erase( it );
 }
diff --git a/radiant/treemodel.cpp b/radiant/treemodel.cpp
index 4b1387f9..9d887db1 100644
--- a/radiant/treemodel.cpp
+++ b/radiant/treemodel.cpp
@@ -743,18 +743,27 @@ void graph_tree_model_row_changed( GraphTreeNode& node );
 
 class GraphTreeNode
 {
-typedef std::map<std::pair<CopiedString, scene::Node*>, GraphTreeNode*> ChildNodes;
+public:
+typedef std::pair<CopiedString, scene::Node*> key_type;
+private:
+struct Compare{
+	bool operator()( const key_type& one, const key_type& other ) const {
+		const int n = string_compare( one.first.c_str(), other.first.c_str() );
+		return n != 0? n < 0 : one.second < other.second;
+	}
+};
+typedef std::map<key_type, GraphTreeNode*, Compare> ChildNodes;
 ChildNodes m_childnodes;
 
-std::list<char> m_list; // dummy list for child index identification
-std::list<char>::const_iterator m_parentListIterator; // iterator from parent's list
+struct Dummy{};
+std::list<Dummy> m_list; // dummy list for child index identification
+std::list<Dummy>::const_iterator m_parentListIterator; // iterator from parent's list
 bool m_searchFromEnd = false; //silly optimization
 public:
 Reference<scene::Instance> m_instance;
 GraphTreeNode* m_parent;
 
 typedef ChildNodes::iterator iterator;
-typedef ChildNodes::key_type key_type;
 typedef ChildNodes::value_type value_type;
 typedef ChildNodes::size_type size_type;
 
@@ -794,10 +803,11 @@ int getIndex() const {
 }
 
 iterator insert( const value_type& value ){
-	iterator i = m_childnodes.insert( value ).first;
+	auto [ i, inserted ] = m_childnodes.insert( value );
+	ASSERT_MESSAGE( inserted, "GraphTreeNode::insert: already added" );
 	( *i ).second->m_parent = this;
 	const auto pos = std::next( i ) == end()? m_list.end() : std::next( i )->second->m_parentListIterator;
-	i->second->m_parentListIterator = m_list.insert( pos, 'a' );
+	i->second->m_parentListIterator = m_list.insert( pos, Dummy() );
 	return i;
 }
 void erase( iterator i ){