diff --git a/Doxyfile b/Doxyfile
index 4f8d9c93b..eaadb283d 100644
--- a/Doxyfile
+++ b/Doxyfile
@@ -1469,7 +1469,7 @@ ENABLE_PREPROCESSING   = YES
 # compilation will be performed. Macro expansion can be done in a controlled
 # way by setting EXPAND_ONLY_PREDEF to YES.
 
-MACRO_EXPANSION        = NO
+MACRO_EXPANSION        = YES
 
 # If the EXPAND_ONLY_PREDEF and MACRO_EXPANSION tags are both set to YES
 # then the macro expansion is limited to the macros specified with the
diff --git a/base/Makefile.am b/base/Makefile.am
index f5520d9e6..601d09d50 100644
--- a/base/Makefile.am
+++ b/base/Makefile.am
@@ -21,7 +21,7 @@ libbase_la_SOURCES =  \
 	delegate.h \
 	dictionary.cpp \
 	dictionary.h \
-	event.h \
+	observable.h \
 	exception.cpp \
 	exception.h \
 	fifo.cpp \
diff --git a/base/application.cpp b/base/application.cpp
index 11fc30fe5..de3054477 100644
--- a/base/application.cpp
+++ b/base/application.cpp
@@ -460,12 +460,12 @@ int Application::Run(int argc, char **argv)
 	} else {
 		try {
 			result = Main(m_Arguments);
-		} catch (const Exception& ex) {
+		} catch (const exception& ex) {
 			Application::Instance.reset();
 
 			Application::Log("---");
 			Application::Log("Exception: " + Utility::GetTypeName(ex));
-			Application::Log("Message: " + ex.GetMessage());
+			Application::Log("Message: " + string(ex.what()));
 
 			return EXIT_FAILURE;
 		}
diff --git a/base/base.vcxproj b/base/base.vcxproj
index 3710e309d..bdcca97ad 100644
--- a/base/base.vcxproj
+++ b/base/base.vcxproj
@@ -45,7 +45,7 @@
     <ClInclude Include="cxx11-compat.h" />
     <ClInclude Include="delegate.h" />
     <ClInclude Include="dictionary.h" />
-    <ClInclude Include="event.h" />
+    <ClInclude Include="observable.h" />
     <ClInclude Include="exception.h" />
     <ClInclude Include="fifo.h" />
     <ClInclude Include="i2-base.h" />
diff --git a/base/configcollection.h b/base/configcollection.h
index 1846453c3..a37332ab1 100644
--- a/base/configcollection.h
+++ b/base/configcollection.h
@@ -50,8 +50,8 @@ public:
 
 	void ForEachObject(function<int (const EventArgs&)> callback);
 
-	Event<EventArgs> OnObjectCommitted;
-	Event<EventArgs> OnObjectRemoved;
+	Observable<EventArgs> OnObjectCommitted;
+	Observable<EventArgs> OnObjectRemoved;
 };
 
 }
diff --git a/base/confighive.h b/base/confighive.h
index c137cf6ca..0bb3b708a 100644
--- a/base/confighive.h
+++ b/base/confighive.h
@@ -45,8 +45,8 @@ public:
 	void ForEachObject(const string& type,
 	    function<int (const EventArgs&)> callback);
 
-	Event<EventArgs> OnObjectCommitted;
-	Event<EventArgs> OnObjectRemoved;
+	Observable<EventArgs> OnObjectCommitted;
+	Observable<EventArgs> OnObjectRemoved;
 };
 
 }
diff --git a/base/dictionary.cpp b/base/dictionary.cpp
index e8e626580..90d6c7c06 100644
--- a/base/dictionary.cpp
+++ b/base/dictionary.cpp
@@ -21,65 +21,6 @@
 
 using namespace icinga;
 
-/**
- * Retrieves a value from the dictionary.
- *
- * @param key The key.
- * @param value Pointer to the value.
- * @returns true if the value was retrieved, false otherwise.
- */
-bool Dictionary::GetProperty(string key, Variant *value) const
-{
-	ConstDictionaryIterator i = m_Data.find(key);
-
-	if (i == m_Data.end())
-		return false;
-
-	*value = i->second;
-	return true;
-}
-
-/**
- * Sets a value in the dictionary.
- *
- * @param key The key.
- * @param value The value.
- */
-void Dictionary::SetProperty(string key, const Variant& value)
-{
-	DictionaryIterator i = m_Data.find(key);
-
-	Variant oldValue;
-	if (i != m_Data.end()) {
-		oldValue = i->second;
-		m_Data.erase(i);
-	}
-
-	m_Data[key] = value;
-}
-
-/**
- * Retrieves a value from the dictionary.
- *
- * @param key The key.
- * @param value Pointer to the value.
- * @returns true if the value was retrieved, false otherwise.
- */
-bool Dictionary::GetProperty(string key, Dictionary::Ptr *value) const
-{
-	Object::Ptr object;
-
-	if (!GetProperty(key, &object))
-		return false;
-
-	Dictionary::Ptr dictionary = dynamic_pointer_cast<Dictionary>(object);
-	if (!dictionary)
-		throw InvalidArgumentException();
-
-	*value = dictionary;
-	return true;
-}
-
 /**
  * Returns an iterator to the beginning of the dictionary.
  *
@@ -109,25 +50,3 @@ long Dictionary::GetLength(void) const
 {
 	return m_Data.size();
 }
-
-/**
- * Adds an unnamed value to the dictionary.
- *
- * @param value The value.
- */
-void Dictionary::AddUnnamedProperty(const Variant& value)
-{
-	map<string, Variant>::const_iterator it;
-	string key;
-	long index = GetLength();
-	do {
-		stringstream s;
-		s << "_" << index;
-		index++;
-
-		key = s.str();
-		it = m_Data.find(key);
-	} while (it != m_Data.end());
-
-	m_Data[key] = value;
-}
diff --git a/base/dictionary.h b/base/dictionary.h
index edfeda281..ec8df2451 100644
--- a/base/dictionary.h
+++ b/base/dictionary.h
@@ -38,29 +38,64 @@ public:
 	typedef shared_ptr<Dictionary> Ptr;
 	typedef weak_ptr<Dictionary> WeakPtr;
 
-	bool GetProperty(string key, Variant *value) const;
-	void SetProperty(string key, const Variant& value);
-
+	/**
+	 * Retrieves a value from the dictionary.
+	 *
+	 * @param key The key.
+	 * @param value Pointer to the value.
+	 * @returns true if the value was retrieved, false otherwise.
+	 */
 	template<typename T>
 	bool GetProperty(string key, T *value) const
 	{
-		Variant data;
+		ConstDictionaryIterator i = m_Data.find(key);
 
-		if (!GetProperty(key, &data))
+		if (i == m_Data.end())
 			return false;
 
-		*value = data;
+		*value = i->second;
 
 		return true;
 	}
 
-	bool GetProperty(string key, Dictionary::Ptr *value) const;
+	/**
+	 * Sets a value in the dictionary.
+	 *
+	 * @param key The key.
+	 * @param value The value.
+	 */
+	template<typename T>
+	void SetProperty(string key, const T& value)
+	{
+		m_Data[key] = value;
+	}
+
+	/**
+	 * Adds an unnamed value to the dictionary.
+	 *
+	 * @param value The value.
+	 */
+	template<typename T>
+	void AddUnnamedProperty(const T& value)
+	{
+		DictionaryIterator it;
+		string key;
+		long index = GetLength();
+		do {
+			stringstream s;
+			s << "_" << index;
+			index++;
+
+			key = s.str();
+			it = m_Data.find(key);
+		} while (it != m_Data.end());
+
+		SetProperty(key, value);
+	}
 
 	DictionaryIterator Begin(void);
 	DictionaryIterator End(void);
 
-	void AddUnnamedProperty(const Variant& value);
-
 	long GetLength(void) const;
 };
 
diff --git a/base/event.h b/base/event.h
deleted file mode 100644
index 430f7b06b..000000000
--- a/base/event.h
+++ /dev/null
@@ -1,92 +0,0 @@
-/******************************************************************************
- * Icinga 2                                                                   *
- * Copyright (C) 2012 Icinga Development Team (http://www.icinga.org/)        *
- *                                                                            *
- * This program is free software; you can redistribute it and/or              *
- * modify it under the terms of the GNU General Public License                *
- * as published by the Free Software Foundation; either version 2             *
- * of the License, or (at your option) any later version.                     *
- *                                                                            *
- * This program is distributed in the hope that it will be useful,            *
- * but WITHOUT ANY WARRANTY; without even the implied warranty of             *
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the              *
- * GNU General Public License for more details.                               *
- *                                                                            *
- * You should have received a copy of the GNU General Public License          *
- * along with this program; if not, write to the Free Software Foundation     *
- * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA.             *
- ******************************************************************************/
-
-#ifndef EVENT_H
-#define EVENT_H
-
-namespace icinga
-{
-
-/**
- * Base class for event arguments.
- */
-struct I2_BASE_API EventArgs
-{
-	Object::Ptr Source; /**< The source of the event. */
-};
-
-/**
- * An observable event.
- */
-template<class TArgs>
-class Event
-{
-public:
-	typedef function<int (const TArgs&)> ObserverType;
-
-private:
-	vector<ObserverType> m_Observers;
-
-public:
-	/**
-	 * Adds an observer to this event.
-	 *
-	 * @param rhs The delegate.
-	 */
-	Event<TArgs>& operator +=(const ObserverType& rhs)
-	{
-		m_Observers.push_back(rhs);
-		return *this;
-	}
-
-	/**
-	 * Removes an observer from this event.
-	 *
-	 * @param rhs The delegate.
-	 */
-	Event<TArgs>& operator -=(const ObserverType& rhs)
-	{
-		m_Observers.erase(rhs);
-		return *this;
-	}
-
-	/**
-	 * Invokes each observer function that is registered for this event. Any
-	 * observer function which returns -1 is removed.
-	 *
-	 * @param args Event arguments.
-	 */
-	void operator()(const TArgs& args)
-	{
-		typename vector<ObserverType>::iterator i;
-
-		for (i = m_Observers.begin(); i != m_Observers.end(); ) {
-			int result = (*i)(args);
-
-			if (result == -1)
-				i = m_Observers.erase(i);
-			else
-				i++;
-		}
-	}
-};
-
-}
-
-#endif /* EVENT_H */
diff --git a/base/exception.cpp b/base/exception.cpp
index 8a339f29e..8f8af1ed3 100644
--- a/base/exception.cpp
+++ b/base/exception.cpp
@@ -33,7 +33,7 @@ Exception::Exception(void)
  *
  * @param message A message describing the exception.
  */
-Exception::Exception(const string& message)
+Exception::Exception(const char *message)
 {
 	SetMessage(message);
 }
@@ -43,19 +43,32 @@ Exception::Exception(const string& message)
  *
  * @returns The description.
  */
-string Exception::GetMessage(void) const
+const char *Exception::GetMessage(void) const
 {
 	return m_Message;
 }
 
+/**
+ * Retrieves the description for the exception.
+ *
+ * @returns The description.
+ */
+const char *Exception::what(void) const throw()
+{
+	return GetMessage();
+}
+
 /**
  * Sets the description for the exception.
  *
  * @param message The description.
  */
-void Exception::SetMessage(string message)
+void Exception::SetMessage(const char *message)
 {
-	m_Message = message;
+	if (m_Message)
+		delete m_Message;
+
+	m_Message = Memory::StrDup(message);
 }
 
 #ifdef _WIN32
diff --git a/base/exception.h b/base/exception.h
index 21c8dd2e7..9687b7341 100644
--- a/base/exception.h
+++ b/base/exception.h
@@ -26,26 +26,29 @@ namespace icinga
 /**
  * Base class for all exceptions.
  */
-class I2_BASE_API Exception
+class I2_BASE_API Exception : exception
 {
 private:
-	string m_Message;
+	const char *m_Message;
 
 protected:
-	void SetMessage(string message);
+	void SetMessage(const char *message);
 
 public:
 	Exception(void);
-	Exception(const string& message);
+	Exception(const char *message);
 
 	/**
 	 * Destructor for the Exception class. Must be virtual for RTTI to work.
 	 */
 	virtual ~Exception(void)
 	{
+		delete m_Message;
 	}
 
-	string GetMessage(void) const;
+	const char *GetMessage(void) const;
+
+	virtual const char *what(void) const throw();
 };
 
 #define DEFINE_EXCEPTION_CLASS(klass)					\
@@ -56,7 +59,7 @@ public:
 		{							\
 		}							\
 									\
-		inline klass(const string& message)			\
+		inline klass(const char *message)			\
 		    : Exception(message)				\
 		{							\
 		}							\
@@ -64,6 +67,7 @@ public:
 
 DEFINE_EXCEPTION_CLASS(NotImplementedException);
 DEFINE_EXCEPTION_CLASS(InvalidArgumentException);
+DEFINE_EXCEPTION_CLASS(InvalidCastException);
 
 #ifdef _WIN32
 /**
@@ -80,7 +84,8 @@ public:
 	 */
 	inline Win32Exception(const string& message, int errorCode)
 	{
-		SetMessage(message + ": " + FormatErrorCode(errorCode));
+		string msg = message + ": " + FormatErrorCode(errorCode);
+		SetMessage(msg.c_str());
 	}
 
 	/**
@@ -107,7 +112,8 @@ public:
 	 */
 	inline PosixException(const string& message, int errorCode)
 	{
-		SetMessage(message + ": " + FormatErrorCode(errorCode));
+		string msg = message + ": " + FormatErrorCode(errorCode);
+		SetMessage(msg.c_str());
 	}
 
 	/**
@@ -133,7 +139,8 @@ public:
 	 */
 	inline OpenSSLException(const string& message, int errorCode)
 	{
-		SetMessage(message + ": " + FormatErrorCode(errorCode));
+		string msg = message + ": " + FormatErrorCode(errorCode);
+		SetMessage(msg.c_str());
 	}
 
 	/**
diff --git a/base/i2-base.h b/base/i2-base.h
index 771708887..985565e89 100644
--- a/base/i2-base.h
+++ b/base/i2-base.h
@@ -103,7 +103,7 @@ using namespace std::tr1::placeholders;
 #include "exception.h"
 #include "memory.h"
 #include "delegate.h"
-#include "event.h"
+#include "observable.h"
 #include "variant.h"
 #include "dictionary.h"
 #include "timer.h"
diff --git a/base/socket.h b/base/socket.h
index ce6b77855..a222913df 100644
--- a/base/socket.h
+++ b/base/socket.h
@@ -62,12 +62,12 @@ public:
 	void SetFD(SOCKET fd);
 	SOCKET GetFD(void) const;
 
-	Event<EventArgs> OnReadable;
-	Event<EventArgs> OnWritable;
-	Event<EventArgs> OnException;
+	Observable<EventArgs> OnReadable;
+	Observable<EventArgs> OnWritable;
+	Observable<EventArgs> OnException;
 
-	Event<SocketErrorEventArgs> OnError;
-	Event<EventArgs> OnClosed;
+	Observable<SocketErrorEventArgs> OnError;
+	Observable<EventArgs> OnClosed;
 
 	virtual bool WantsToRead(void) const;
 	virtual bool WantsToWrite(void) const;
diff --git a/base/tcpclient.h b/base/tcpclient.h
index 5c36dfa33..de7ed3757 100644
--- a/base/tcpclient.h
+++ b/base/tcpclient.h
@@ -64,7 +64,7 @@ public:
 	virtual bool WantsToRead(void) const;
 	virtual bool WantsToWrite(void) const;
 
-	Event<EventArgs> OnDataAvailable;
+	Observable<EventArgs> OnDataAvailable;
 };
 
 /**
diff --git a/base/tcpserver.h b/base/tcpserver.h
index d9b30190d..370cac0d6 100644
--- a/base/tcpserver.h
+++ b/base/tcpserver.h
@@ -54,7 +54,7 @@ public:
 
 	void Listen(void);
 
-	Event<NewClientEventArgs> OnNewClient;
+	Observable<NewClientEventArgs> OnNewClient;
 
 	virtual bool WantsToRead(void) const;
 };
diff --git a/base/thread.cpp b/base/thread.cpp
index 70c2fe2e9..611dbbfaf 100644
--- a/base/thread.cpp
+++ b/base/thread.cpp
@@ -21,12 +21,6 @@
 
 using namespace icinga;
 
-typedef struct threadparam_s
-{
-	ThreadProc callback;
-	void *param;
-} threadparam_t;
-
 /**
  * Helper function that deals with OS-specific differences in the thread
  * proc's function signature.
@@ -34,16 +28,16 @@ typedef struct threadparam_s
 #ifdef _WIN32
 static DWORD WINAPI ThreadStartProc(LPVOID param)
 {
-	threadparam_t *tparam = (threadparam_t *)param;
-	tparam->callback(tparam->param);
+	ThreadParameters *tparam = (ThreadParameters *)param;
+	tparam->Callback(tparam->UserParams);
 	delete tparam;
 	return 0;
 }
 #else /* _WIN32 */
 static void *ThreadStartProc(void *param)
 {
-	threadparam_t *tparam = (threadparam_t *)param;
-	tparam->callback(tparam->param);
+	ThreadParameters *tparam = (ThreadParameters *)param;
+	tparam->Callback(tparam->UserParams);
 	delete tparam;
 	return NULL;
 }
@@ -55,13 +49,13 @@ static void *ThreadStartProc(void *param)
  */
 Thread::Thread(ThreadProc callback, void *param)
 {
-	threadparam_t *tparam = new threadparam_t();
+	ThreadParameters *tparam = new ThreadParameters();
 
 	if (tparam == NULL)
 		throw OutOfMemoryException("Out of memory");
 
-	tparam->callback = callback;
-	tparam->param = param;
+	tparam->Callback = callback;
+	tparam->UserParams = param;
 
 #ifdef _WIN32
 	m_Thread = CreateThread(NULL, 0, ThreadStartProc, tparam, CREATE_SUSPENDED, NULL);
@@ -69,7 +63,8 @@ Thread::Thread(ThreadProc callback, void *param)
 	if (m_Thread == NULL)
 		throw Win32Exception("CreateThread failed.", GetLastError());
 #else /* _WIN32 */
-	pthread_create(&m_Thread, NULL, ThreadStartProc, &tparam);
+	if (pthread_create(&m_Thread, NULL, ThreadStartProc, &tparam) < 0)
+		throw PosixException("pthread_create failed.", errno);
 #endif /* _WIN32 */
 }
 
diff --git a/base/thread.h b/base/thread.h
index cf6744a25..7f3237025 100644
--- a/base/thread.h
+++ b/base/thread.h
@@ -25,6 +25,12 @@ namespace icinga
 
 typedef void (*ThreadProc)(void *);
 
+struct ThreadParameters
+{
+	ThreadProc Callback;
+	void *UserParams;
+};
+
 /**
  * A wrapper around OS-specific thread functionality.
  */
diff --git a/base/timer.h b/base/timer.h
index 79f013d53..17017a9f3 100644
--- a/base/timer.h
+++ b/base/timer.h
@@ -72,7 +72,7 @@ public:
 
 	void Reschedule(time_t next);
 
-	Event<TimerEventArgs> OnTimerExpired;
+	Observable<TimerEventArgs> OnTimerExpired;
 };
 
 }
diff --git a/base/tlsclient.h b/base/tlsclient.h
index bf76dbe16..cec54277c 100644
--- a/base/tlsclient.h
+++ b/base/tlsclient.h
@@ -73,7 +73,7 @@ public:
 	virtual bool WantsToRead(void) const;
 	virtual bool WantsToWrite(void) const;
 
-	Event<VerifyCertificateEventArgs> OnVerifyCertificate;
+	Observable<VerifyCertificateEventArgs> OnVerifyCertificate;
 };
 
 TCPClient::Ptr TLSClientFactory(TCPClientRole role, shared_ptr<SSL_CTX> sslContext);
diff --git a/components/discovery/discoverycomponent.cpp b/components/discovery/discoverycomponent.cpp
index b1fa37277..0dade5e88 100644
--- a/components/discovery/discoverycomponent.cpp
+++ b/components/discovery/discoverycomponent.cpp
@@ -357,10 +357,14 @@ bool DiscoveryComponent::HasMessagePermission(Dictionary::Ptr roles, string mess
 		if (!role)
 			continue;
 
-		Dictionary::Ptr permissions;
-		if (!role->GetProperty(messageType, &permissions))
+		Object::Ptr object;
+		if (!role->GetProperty(messageType, &object))
 			continue;
 
+		Dictionary::Ptr permissions = dynamic_pointer_cast<Dictionary>(object);
+		if (!permissions)
+			throw InvalidCastException();
+
 		for (DictionaryIterator is = permissions->Begin(); is != permissions->End(); is++) {
 			if (Utility::Match(is->second.GetString(), message))
 				return true;
@@ -396,8 +400,15 @@ void DiscoveryComponent::ProcessDiscoveryMessage(string identity, DiscoveryMessa
 
 	ConfigObject::Ptr endpointConfig = endpointCollection->GetObject(identity);
 	Dictionary::Ptr roles;
-	if (endpointConfig)
-		endpointConfig->GetProperty("roles", &roles);
+	if (endpointConfig) {
+		Object::Ptr object;
+		if (endpointConfig->GetProperty("roles", &object)) {
+			roles = dynamic_pointer_cast<Dictionary>(object);
+
+			if (!roles)
+				throw InvalidCastException();
+		}
+	}
 
 	Endpoint::Ptr endpoint = GetEndpointManager()->GetEndpointByIdentity(identity);
 
diff --git a/icinga/endpoint.h b/icinga/endpoint.h
index 71939675a..59f046c85 100644
--- a/icinga/endpoint.h
+++ b/icinga/endpoint.h
@@ -92,8 +92,8 @@ public:
 	ConstTopicIterator BeginPublications(void) const;
 	ConstTopicIterator EndPublications(void) const;
 
-	Event<EventArgs> OnIdentityChanged;
-	Event<EventArgs> OnSessionEstablished;
+	Observable<EventArgs> OnIdentityChanged;
+	Observable<EventArgs> OnSessionEstablished;
 };
 
 }
diff --git a/icinga/endpointmanager.h b/icinga/endpointmanager.h
index d7cd71c22..f6e322638 100644
--- a/icinga/endpointmanager.h
+++ b/icinga/endpointmanager.h
@@ -71,7 +71,7 @@ public:
 
 	Endpoint::Ptr GetEndpointByIdentity(string identity) const;
 
-	Event<NewEndpointEventArgs> OnNewEndpoint;
+	Observable<NewEndpointEventArgs> OnNewEndpoint;
 };
 
 }
diff --git a/icinga/virtualendpoint.cpp b/icinga/virtualendpoint.cpp
index d36426b09..48e48ab2a 100644
--- a/icinga/virtualendpoint.cpp
+++ b/icinga/virtualendpoint.cpp
@@ -60,7 +60,7 @@ void VirtualEndpoint::ProcessRequest(Endpoint::Ptr sender, const RpcRequest& req
 	if (!request.GetMethod(&method))
 		return;
 
-	map<string, Event<NewRequestEventArgs> >::iterator i = m_TopicHandlers.find(method);
+	map<string, Observable<NewRequestEventArgs> >::iterator i = m_TopicHandlers.find(method);
 
 	if (i == m_TopicHandlers.end())
 		return;
diff --git a/icinga/virtualendpoint.h b/icinga/virtualendpoint.h
index c7774d556..5222502d5 100644
--- a/icinga/virtualendpoint.h
+++ b/icinga/virtualendpoint.h
@@ -38,7 +38,7 @@ struct I2_ICINGA_API NewRequestEventArgs : public EventArgs
 class I2_ICINGA_API VirtualEndpoint : public Endpoint
 {
 private:
-	map< string, Event<NewRequestEventArgs> > m_TopicHandlers;
+	map< string, Observable<NewRequestEventArgs> > m_TopicHandlers;
 
 public:
 	typedef shared_ptr<VirtualEndpoint> Ptr;
diff --git a/jsonrpc/jsonrpcclient.cpp b/jsonrpc/jsonrpcclient.cpp
index 42dafe9d8..c240946ad 100644
--- a/jsonrpc/jsonrpcclient.cpp
+++ b/jsonrpc/jsonrpcclient.cpp
@@ -53,7 +53,7 @@ int JsonRpcClient::DataAvailableHandler(const EventArgs&)
 			nea.Message = message;
 			OnNewMessage(nea);
 		} catch (const Exception& ex) {
-			Application::Log("Exception while processing message from JSON-RPC client: " + ex.GetMessage());
+			Application::Log("Exception while processing message from JSON-RPC client: " + string(ex.GetMessage()));
 			Close();
 
 			return 1;
diff --git a/jsonrpc/jsonrpcclient.h b/jsonrpc/jsonrpcclient.h
index 9f7d242ba..07aac91de 100644
--- a/jsonrpc/jsonrpcclient.h
+++ b/jsonrpc/jsonrpcclient.h
@@ -46,7 +46,7 @@ public:
 
 	virtual void Start(void);
 
-	Event<NewMessageEventArgs> OnNewMessage;
+	Observable<NewMessageEventArgs> OnNewMessage;
 };
 
 TCPClient::Ptr JsonRpcClientFactory(TCPClientRole role, shared_ptr<SSL_CTX> sslContext);
diff --git a/jsonrpc/messagepart.cpp b/jsonrpc/messagepart.cpp
index bd1446326..de701dc3f 100644
--- a/jsonrpc/messagepart.cpp
+++ b/jsonrpc/messagepart.cpp
@@ -130,10 +130,14 @@ Dictionary::Ptr MessagePart::GetDictionary(void) const
 
 bool MessagePart::GetProperty(string key, MessagePart *value) const
 {
-	Dictionary::Ptr dictionary;
-	if (!GetDictionary()->GetProperty(key, &dictionary))
+	Object::Ptr object;
+	if (GetDictionary()->GetProperty(key, &object))
 		return false;
 
+	Dictionary::Ptr dictionary = dynamic_pointer_cast<Dictionary>(object);
+	if (!dictionary)
+		throw InvalidCastException();
+
 	*value = MessagePart(dictionary);
 	return true;
 }