diff --git a/lib/cli/objectlistcommand.cpp b/lib/cli/objectlistcommand.cpp
index 7d48075e8..951dd12b8 100644
--- a/lib/cli/objectlistcommand.cpp
+++ b/lib/cli/objectlistcommand.cpp
@@ -188,10 +188,12 @@ void ObjectListCommand::PrintHints(std::ostream& fp, const Dictionary::Ptr& debu
 
 	Array::Ptr messages = debug_hints->Get("messages");
 
-	ObjectLock olock(messages);
+	if (messages) {
+		ObjectLock olock(messages);
 
-	BOOST_FOREACH(const Value& msg, messages) {
-		PrintHint(fp, msg, indent);
+		BOOST_FOREACH(const Value& msg, messages) {
+			PrintHint(fp, msg, indent);
+		}
 	}
 }
 
diff --git a/lib/config/expression.cpp b/lib/config/expression.cpp
index f80c0fc08..13c587ec3 100644
--- a/lib/config/expression.cpp
+++ b/lib/config/expression.cpp
@@ -282,7 +282,8 @@ Value DictExpression::DoEvaluate(const Object::Ptr& context, DebugHint *dhint) c
 
 Value SetExpression::DoEvaluate(const Object::Ptr& context, DebugHint *dhint) const
 {
-	DebugHint *sdhint = dhint;
+	DebugHint *psdhint = dhint;
+	DebugHint sdhint;
 
 	Value parent, object;
 	String index;
@@ -291,8 +292,10 @@ Value SetExpression::DoEvaluate(const Object::Ptr& context, DebugHint *dhint) co
 		Expression *indexExpr = m_Indexer[i];
 		String tempindex = indexExpr->Evaluate(context, dhint);
 
-		if (sdhint)
-			sdhint = sdhint->GetChild(tempindex);
+		if (psdhint) {
+			sdhint = psdhint->GetChild(tempindex);
+			psdhint = &sdhint;
+		}
 
 		if (i == 0)
 			parent = context;
@@ -311,7 +314,7 @@ Value SetExpression::DoEvaluate(const Object::Ptr& context, DebugHint *dhint) co
 		LiteralExpression *eindex = MakeLiteral(tempindex);
 
 		IndexerExpression eip(eparent, eindex, m_DebugInfo);
-		object = eip.Evaluate(context, sdhint);
+		object = eip.Evaluate(context, psdhint);
 
 		if (i != m_Indexer.size() - 1 && object.IsEmpty()) {
 			object = new Dictionary();
@@ -346,8 +349,8 @@ Value SetExpression::DoEvaluate(const Object::Ptr& context, DebugHint *dhint) co
 
 	SetField(parent, index, right);
 
-	if (sdhint)
-		sdhint->AddMessage("=", m_DebugInfo);
+	if (psdhint)
+		psdhint->AddMessage("=", m_DebugInfo);
 
 	return right;
 }
@@ -524,37 +527,6 @@ Value ForExpression::DoEvaluate(const Object::Ptr& context, DebugHint *dhint) co
 	return Empty;
 }
 
-Dictionary::Ptr DebugHint::ToDictionary(void) const
-{
-	Dictionary::Ptr result = new Dictionary();
-
-	Array::Ptr messages = new Array();
-	typedef std::pair<String, DebugInfo> MessageType;
-	BOOST_FOREACH(const MessageType& message, Messages) {
-		Array::Ptr amsg = new Array();
-		amsg->Add(message.first);
-		amsg->Add(message.second.Path);
-		amsg->Add(message.second.FirstLine);
-		amsg->Add(message.second.FirstColumn);
-		amsg->Add(message.second.LastLine);
-		amsg->Add(message.second.LastColumn);
-		messages->Add(amsg);
-	}
-
-	result->Set("messages", messages);
-
-	Dictionary::Ptr properties = new Dictionary();
-
-	typedef std::map<String, DebugHint>::value_type ChildType;
-	BOOST_FOREACH(const ChildType& kv, Children) {
-		properties->Set(kv.first, kv.second.ToDictionary());
-	}
-
-	result->Set("properties", properties);
-
-	return result;
-}
-
 bool Expression::HasField(const Object::Ptr& context, const String& field)
 {
 	Dictionary::Ptr dict = dynamic_pointer_cast<Dictionary>(context);
diff --git a/lib/config/expression.hpp b/lib/config/expression.hpp
index de618db92..9c2b6fb56 100644
--- a/lib/config/expression.hpp
+++ b/lib/config/expression.hpp
@@ -31,20 +31,60 @@ namespace icinga
 
 struct DebugHint
 {
-	std::vector<std::pair<String, DebugInfo> > Messages;
-	std::map<String, DebugHint> Children;
+public:
+	DebugHint(const Dictionary::Ptr& hints = Dictionary::Ptr())
+		: m_Hints(hints)
+	{ }
 
 	inline void AddMessage(const String& message, const DebugInfo& di)
 	{
-		Messages.push_back(std::make_pair(message, di));
+		if (!m_Hints)
+			m_Hints = new Dictionary();
+
+		if (!m_Messages) {
+			m_Messages = new Array();
+			m_Hints->Set("messages", m_Messages);
+		}
+
+		Array::Ptr amsg = new Array();
+		amsg->Add(message);
+		amsg->Add(di.Path);
+		amsg->Add(di.FirstLine);
+		amsg->Add(di.FirstColumn);
+		amsg->Add(di.LastLine);
+		amsg->Add(di.LastColumn);
+		m_Messages->Add(amsg);
 	}
 
-	inline DebugHint *GetChild(const String& name)
+	inline DebugHint GetChild(const String& name)
 	{
-		return &Children[name];
+		if (!m_Hints)
+			m_Hints = new Dictionary();
+
+		if (!m_Children) {
+			m_Children = new Dictionary;
+			m_Hints->Set("properties", m_Children);
+		}
+
+		Dictionary::Ptr child = m_Children->Get(name);
+
+		if (!child) {
+			child = new Dictionary();
+			m_Children->Set(name, child);
+		}
+
+		return DebugHint(child);
 	}
 
-	Dictionary::Ptr ToDictionary(void) const;
+	Dictionary::Ptr ToDictionary(void) const
+	{
+		return m_Hints;
+	}
+
+private:
+	Dictionary::Ptr m_Hints;
+	Array::Ptr m_Messages;
+	Dictionary::Ptr m_Children;
 };
 
 enum CombinedSetOp