diff --git a/lib/base/array.cpp b/lib/base/array.cpp
index 9d236954b..d9e8ea06c 100644
--- a/lib/base/array.cpp
+++ b/lib/base/array.cpp
@@ -108,6 +108,20 @@ size_t Array::GetLength(void) const
 	return m_Data.size();
 }
 
+/**
+ * Checks whether the array contains the specified value.
+ *
+ * @param value The value.
+ * @returns true if the array contains the value, false otherwise.
+ */
+bool Array::Contains(const String& value) const
+{
+	ASSERT(!OwnsLock());
+	ObjectLock olock(this);
+
+	return (std::find(m_Data.begin(), m_Data.end(), value) != m_Data.end());
+}
+
 /**
  * Insert the given value at the specified index
  *
diff --git a/lib/base/array.h b/lib/base/array.h
index 0e53fbf78..b7e39b0ef 100644
--- a/lib/base/array.h
+++ b/lib/base/array.h
@@ -50,6 +50,7 @@ public:
 	Iterator End(void);
 
 	size_t GetLength(void) const;
+	bool Contains(const String& value) const;
 
 	void Insert(unsigned int index, const Value& value);
 	void Remove(unsigned int index);
diff --git a/lib/config/applyrule.cpp b/lib/config/applyrule.cpp
index a9eba3026..cb73ba229 100644
--- a/lib/config/applyrule.cpp
+++ b/lib/config/applyrule.cpp
@@ -75,7 +75,7 @@ bool ApplyRule::EvaluateFilter(const Dictionary::Ptr& scope) const
 	return result;
 }
 
-void ApplyRule::EvaluateRules(void)
+void ApplyRule::EvaluateRules(bool clear)
 {
 	std::set<String> completedTypes;
 
@@ -113,7 +113,8 @@ void ApplyRule::EvaluateRules(void)
 		}
 	}
 
-	m_Rules.clear();
+	if (clear)
+		m_Rules.clear();
 }
 
 void ApplyRule::RegisterType(const String& sourceType, const std::vector<String>& targetTypes, const ApplyRule::Callback& callback)
diff --git a/lib/config/applyrule.h b/lib/config/applyrule.h
index cdbe4bb3b..8692f718b 100644
--- a/lib/config/applyrule.h
+++ b/lib/config/applyrule.h
@@ -49,7 +49,7 @@ public:
 
 	static void AddRule(const String& sourceType, const String& targetType, const String& name, const AExpression::Ptr& expression,
 	    const AExpression::Ptr& filter, const DebugInfo& di, const Dictionary::Ptr& scope);
-	static void EvaluateRules(void);
+	static void EvaluateRules(bool clear);
 
 	static void RegisterType(const String& sourceType, const std::vector<String>& targetTypes, const ApplyRule::Callback& callback);
 	static bool IsValidSourceType(const String& sourceType);
diff --git a/lib/config/configitem.cpp b/lib/config/configitem.cpp
index 28bf248c9..194fa9c27 100644
--- a/lib/config/configitem.cpp
+++ b/lib/config/configitem.cpp
@@ -316,11 +316,14 @@ bool ConfigItem::ValidateItems(void)
 
 	upq.Join();
 
-	Log(LogInformation, "config", "Evaluating 'apply' rules...");
-	ApplyRule::EvaluateRules();
+	Log(LogInformation, "config", "Evaluating 'object' rules (step 1)...");
+	ObjectRule::EvaluateRules(false);
 
-	Log(LogInformation, "config", "Evaluating 'object' rules...");
-	ObjectRule::EvaluateRules();
+	Log(LogInformation, "config", "Evaluating 'apply' rules...");
+	ApplyRule::EvaluateRules(true);
+
+	Log(LogInformation, "config", "Evaluating 'object' rules (step 2)...");
+	ObjectRule::EvaluateRules(true);
 
 	Log(LogInformation, "config", "Validating config items (step 2)...");
 
diff --git a/lib/config/objectrule.cpp b/lib/config/objectrule.cpp
index a6cc0ab2e..c0c7bc0a7 100644
--- a/lib/config/objectrule.cpp
+++ b/lib/config/objectrule.cpp
@@ -70,7 +70,7 @@ bool ObjectRule::EvaluateFilter(const Dictionary::Ptr& scope) const
 	return result;
 }
 
-void ObjectRule::EvaluateRules(void)
+void ObjectRule::EvaluateRules(bool clear)
 {
 	std::pair<String, Callback> kv;
 	BOOST_FOREACH(kv, m_Callbacks) {
@@ -84,7 +84,8 @@ void ObjectRule::EvaluateRules(void)
 		callback(it->second);
 	}
 
-	m_Rules.clear();
+	if (clear)
+		m_Rules.clear();
 }
 
 void ObjectRule::RegisterType(const String& sourceType, const ObjectRule::Callback& callback)
diff --git a/lib/config/objectrule.h b/lib/config/objectrule.h
index 3f3cbe0b9..530fd35bf 100644
--- a/lib/config/objectrule.h
+++ b/lib/config/objectrule.h
@@ -48,7 +48,7 @@ public:
 
 	static void AddRule(const String& sourceType, const String& name, const AExpression::Ptr& expression,
 	    const AExpression::Ptr& filter, const DebugInfo& di, const Dictionary::Ptr& scope);
-	static void EvaluateRules(void);
+	static void EvaluateRules(bool clear);
 
 	static void RegisterType(const String& sourceType, const ObjectRule::Callback& callback);
 	static bool IsValidSourceType(const String& sourceType);
diff --git a/lib/icinga/checkable.cpp b/lib/icinga/checkable.cpp
index 6bb251eef..d60ffaf44 100644
--- a/lib/icinga/checkable.cpp
+++ b/lib/icinga/checkable.cpp
@@ -88,6 +88,21 @@ void Checkable::OnStateLoaded(void)
 	}
 }
 
+void Checkable::AddGroup(const String& name)
+{
+	boost::mutex::scoped_lock lock(m_CheckableMutex);
+
+	Array::Ptr groups = GetGroups();
+
+	if (groups && groups->Contains(name))
+		return;
+
+	if (!groups)
+		groups = make_shared<Array>();
+
+	groups->Add(name);
+}
+
 AcknowledgementType Checkable::GetAcknowledgement(void)
 {
 	ASSERT(OwnsLock());
diff --git a/lib/icinga/checkable.h b/lib/icinga/checkable.h
index 8d4f1c673..e068d2477 100644
--- a/lib/icinga/checkable.h
+++ b/lib/icinga/checkable.h
@@ -89,6 +89,8 @@ public:
 	std::set<Checkable::Ptr> GetParents(void) const;
 	std::set<Checkable::Ptr> GetChildren(void) const;
 
+	void AddGroup(const String& name);
+
 	//bool IsHostCheck(void) const;
 
 	bool IsReachable(DependencyType dt = DependencyState, shared_ptr<Dependency> *failedDependency = NULL, int rstack = 0) const;
@@ -270,6 +272,7 @@ protected:
 	virtual void OnStateLoaded(void);
 
 private:
+	mutable boost::mutex m_CheckableMutex;
 	bool m_CheckRunning;
 	long m_SchedulingOffset;
 
diff --git a/lib/icinga/checkable.ti b/lib/icinga/checkable.ti
index dd2fade39..380ff9ff2 100644
--- a/lib/icinga/checkable.ti
+++ b/lib/icinga/checkable.ti
@@ -1,5 +1,6 @@
 #include "icinga/icingaapplication.h"
 #include "base/dynamicobject.h"
+#include "base/array.h"
 
 namespace icinga
 {
@@ -20,7 +21,9 @@ enum AcknowledgementType
 
 abstract class Checkable : DynamicObject
 {
-	[config] Array::Ptr groups;
+	[config] Array::Ptr groups {
+		default {{{ return make_shared<Array>(); }}}
+	};
 	[config, protected] String check_command (CheckCommandRaw);
 	[config] int max_check_attempts (MaxCheckAttemptsRaw) {
 		default {{{ return 3; }}}
diff --git a/lib/icinga/host.ti b/lib/icinga/host.ti
index a45493258..1a8c3ed83 100644
--- a/lib/icinga/host.ti
+++ b/lib/icinga/host.ti
@@ -14,7 +14,6 @@ class Host : Checkable
 				return m_DisplayName;
 		}}}
 	};
-	[config] Array::Ptr groups;
 
 	[config] String address;
 	[config] String address6;
diff --git a/lib/icinga/hostgroup.cpp b/lib/icinga/hostgroup.cpp
index cc6d2ac6e..d57de68cb 100644
--- a/lib/icinga/hostgroup.cpp
+++ b/lib/icinga/hostgroup.cpp
@@ -66,6 +66,9 @@ bool HostGroup::EvaluateObjectRule(const Host::Ptr host, const ObjectRule& rule)
 	/* assign host group membership */
 	group->ResolveGroupMembership(host, true);
 
+	/* update groups attribute for apply */
+	host->AddGroup(group_name);
+
 	return true;
 }
 
diff --git a/lib/icinga/servicegroup.cpp b/lib/icinga/servicegroup.cpp
index 09f82cc43..9a2d0bcb5 100644
--- a/lib/icinga/servicegroup.cpp
+++ b/lib/icinga/servicegroup.cpp
@@ -70,6 +70,9 @@ bool ServiceGroup::EvaluateObjectRule(const Service::Ptr service, const ObjectRu
 	/* assign service group membership */
 	group->ResolveGroupMembership(service, true);
 
+	/* update groups attribute for apply */
+	service->AddGroup(group_name);
+
 	return true;
 }
 
diff --git a/lib/icinga/user.cpp b/lib/icinga/user.cpp
index 6834574bf..71ab946b8 100644
--- a/lib/icinga/user.cpp
+++ b/lib/icinga/user.cpp
@@ -69,6 +69,21 @@ void User::Stop(void)
 	}
 }
 
+void User::AddGroup(const String& name)
+{
+	boost::mutex::scoped_lock lock(m_UserMutex);
+
+	Array::Ptr groups = GetGroups();
+
+	if (groups && groups->Contains(name))
+		return;
+
+	if (!groups)
+		groups = make_shared<Array>();
+
+	groups->Add(name);
+}
+
 TimePeriod::Ptr User::GetPeriod(void) const
 {
 	return TimePeriod::GetByName(GetPeriodRaw());
diff --git a/lib/icinga/user.h b/lib/icinga/user.h
index d5b441ca6..780cd979f 100644
--- a/lib/icinga/user.h
+++ b/lib/icinga/user.h
@@ -40,6 +40,8 @@ public:
 	DECLARE_PTR_TYPEDEFS(User);
 	DECLARE_TYPENAME(User);
 
+	void AddGroup(const String& name);
+
 	/* Notifications */
 	TimePeriod::Ptr GetPeriod(void) const;
 
@@ -52,6 +54,8 @@ protected:
 	virtual void Stop(void);
 
 	virtual void OnConfigLoaded(void);
+private:
+	mutable boost::mutex m_UserMutex;
 };
 
 }
diff --git a/lib/icinga/user.ti b/lib/icinga/user.ti
index 2c25a7631..052c16151 100644
--- a/lib/icinga/user.ti
+++ b/lib/icinga/user.ti
@@ -1,4 +1,5 @@
 #include "base/dynamicobject.h"
+#include "base/array.h"
 
 namespace icinga
 {
@@ -13,7 +14,9 @@ class User : DynamicObject
 				return m_DisplayName;
 		}}}
 	};
-	[config] Array::Ptr groups;
+	[config] Array::Ptr groups {
+		default {{{ return make_shared<Array>(); }}}
+	};
 	[config] String period (PeriodRaw);
 	[config] Array::Ptr types;
 	int type_filter_real (TypeFilter);
diff --git a/lib/icinga/usergroup.cpp b/lib/icinga/usergroup.cpp
index 2ee963709..1735d24a6 100644
--- a/lib/icinga/usergroup.cpp
+++ b/lib/icinga/usergroup.cpp
@@ -66,6 +66,9 @@ bool UserGroup::EvaluateObjectRule(const User::Ptr user, const ObjectRule& rule)
 	/* assign user group membership */
 	group->ResolveGroupMembership(user, true);
 
+	/* update groups attribute for apply */
+	user->AddGroup(group_name);
+
 	return true;
 }