diff --git a/lib/icinga/hostgroup.cpp b/lib/icinga/hostgroup.cpp
index 92ba03873..0d0899e05 100644
--- a/lib/icinga/hostgroup.cpp
+++ b/lib/icinga/hostgroup.cpp
@@ -32,6 +32,7 @@ static boost::mutex l_Mutex;
 static std::map<String, std::vector<Host::WeakPtr> > l_MembersCache;
 static bool l_MembersCacheNeedsUpdate = false;
 static Timer::Ptr l_MembersCacheTimer;
+boost::signals2::signal<void (void)> HostGroup::OnMembersChanged;
 
 REGISTER_TYPE(HostGroup);
 
@@ -139,4 +140,6 @@ void HostGroup::RefreshMembersCache(void)
 
 	boost::mutex::scoped_lock lock(l_Mutex);
 	l_MembersCache.swap(newMembersCache);
+
+	OnMembersChanged();
 }
diff --git a/lib/icinga/hostgroup.h b/lib/icinga/hostgroup.h
index dcfd4b5cb..a9e1aef4b 100644
--- a/lib/icinga/hostgroup.h
+++ b/lib/icinga/hostgroup.h
@@ -49,6 +49,8 @@ public:
 
 	static void InvalidateMembersCache(void);
 
+	static boost::signals2::signal<void (void)> OnMembersChanged;
+
 protected:
 	virtual void OnRegistrationCompleted(void);