diff --git a/icinga/endpointmanager.cpp b/icinga/endpointmanager.cpp
index 9159d2f01..12a95c597 100644
--- a/icinga/endpointmanager.cpp
+++ b/icinga/endpointmanager.cpp
@@ -39,7 +39,7 @@ EndpointManager::EndpointManager(void)
  *
  * @param identity The new identity.
  */
-void EndpointManager::SetIdentity(string identity)
+void EndpointManager::SetIdentity(const string& identity)
 {
 	m_Identity = identity;
 }
@@ -59,7 +59,7 @@ string EndpointManager::GetIdentity(void) const
  *
  * @param sslContext The new SSL context.
  */
-void EndpointManager::SetSSLContext(shared_ptr<SSL_CTX> sslContext)
+void EndpointManager::SetSSLContext(const shared_ptr<SSL_CTX>& sslContext)
 {
 	m_SSLContext = sslContext;
 }
@@ -79,7 +79,7 @@ shared_ptr<SSL_CTX> EndpointManager::GetSSLContext(void) const
  *
  * @param service The port to listen on.
  */
-void EndpointManager::AddListener(string service)
+void EndpointManager::AddListener(const string& service)
 {
 	if (!GetSSLContext())
 		throw_exception(logic_error("SSL context is required for AddListener()"));
@@ -102,7 +102,7 @@ void EndpointManager::AddListener(string service)
  * @param node The remote host.
  * @param service The remote port.
  */
-void EndpointManager::AddConnection(string node, string service)
+void EndpointManager::AddConnection(const string& node, const string& service)
 {
 	stringstream s;
 	s << "Adding new endpoint: [" << node << "]:" << service;
@@ -118,7 +118,7 @@ void EndpointManager::AddConnection(string node, string service)
  *
  * @param server The JSON-RPC server.
  */
-void EndpointManager::RegisterServer(JsonRpcServer::Ptr server)
+void EndpointManager::RegisterServer(const JsonRpcServer::Ptr& server)
 {
 	m_Servers.push_back(server);
 	server->OnNewClient.connect(boost::bind(&EndpointManager::NewClientHandler,
@@ -145,7 +145,7 @@ void EndpointManager::NewClientHandler(const TcpClient::Ptr& client)
  *
  * @param server The JSON-RPC server.
  */
-void EndpointManager::UnregisterServer(JsonRpcServer::Ptr server)
+void EndpointManager::UnregisterServer(const JsonRpcServer::Ptr& server)
 {
 	m_Servers.erase(
 	    remove(m_Servers.begin(), m_Servers.end(), server),
@@ -158,7 +158,7 @@ void EndpointManager::UnregisterServer(JsonRpcServer::Ptr server)
  *
  * @param endpoint The new endpoint.
  */
-void EndpointManager::RegisterEndpoint(Endpoint::Ptr endpoint)
+void EndpointManager::RegisterEndpoint(const Endpoint::Ptr& endpoint)
 {
 	endpoint->SetEndpointManager(GetSelf());
 
@@ -194,7 +194,7 @@ void EndpointManager::RegisterEndpoint(Endpoint::Ptr endpoint)
  *
  * @param endpoint The endpoint.
  */
-void EndpointManager::UnregisterEndpoint(Endpoint::Ptr endpoint)
+void EndpointManager::UnregisterEndpoint(const Endpoint::Ptr& endpoint)
 {
 	m_PendingEndpoints.erase(
 	    remove(m_PendingEndpoints.begin(), m_PendingEndpoints.end(), endpoint),
@@ -212,8 +212,8 @@ void EndpointManager::UnregisterEndpoint(Endpoint::Ptr endpoint)
  * @param recipient The recipient of the message.
  * @param message The request.
  */
-void EndpointManager::SendUnicastMessage(Endpoint::Ptr sender,
-    Endpoint::Ptr recipient, const MessagePart& message)
+void EndpointManager::SendUnicastMessage(const Endpoint::Ptr& sender,
+    const Endpoint::Ptr& recipient, const MessagePart& message)
 {
 	/* don't forward messages between non-local endpoints */
 	if (!sender->IsLocal() && !recipient->IsLocal())
@@ -232,7 +232,7 @@ void EndpointManager::SendUnicastMessage(Endpoint::Ptr sender,
  * @param sender The sender of the message.
  * @param message The message.
  */
-void EndpointManager::SendAnycastMessage(Endpoint::Ptr sender,
+void EndpointManager::SendAnycastMessage(const Endpoint::Ptr& sender,
     const RequestMessage& message)
 {
 	string method;
@@ -264,7 +264,7 @@ void EndpointManager::SendAnycastMessage(Endpoint::Ptr sender,
  * @param sender The sender of the message.
  * @param message The message.
  */
-void EndpointManager::SendMulticastMessage(Endpoint::Ptr sender,
+void EndpointManager::SendMulticastMessage(const Endpoint::Ptr& sender,
     const RequestMessage& message)
 {
 	string id;
@@ -307,7 +307,7 @@ void EndpointManager::ForEachEndpoint(function<void (const EndpointManager::Ptr&
  *
  * @param identity The identity of the endpoint.
  */
-Endpoint::Ptr EndpointManager::GetEndpointByIdentity(string identity) const
+Endpoint::Ptr EndpointManager::GetEndpointByIdentity(const string& identity) const
 {
 	map<string, Endpoint::Ptr>::const_iterator i;
 	i = m_Endpoints.find(identity);
diff --git a/icinga/endpointmanager.h b/icinga/endpointmanager.h
index 7a89c660d..e539072b1 100644
--- a/icinga/endpointmanager.h
+++ b/icinga/endpointmanager.h
@@ -40,21 +40,21 @@ public:
 
 	static EndpointManager::Ptr GetInstance(void);
 
-	void SetIdentity(string identity);
+	void SetIdentity(const string& identity);
 	string GetIdentity(void) const;
 
-	void SetSSLContext(shared_ptr<SSL_CTX> sslContext);
+	void SetSSLContext(const shared_ptr<SSL_CTX>& sslContext);
 	shared_ptr<SSL_CTX> GetSSLContext(void) const;
 
-	void AddListener(string service);
-	void AddConnection(string node, string service);
+	void AddListener(const string& service);
+	void AddConnection(const string& node, const string& service);
 
-	void RegisterEndpoint(Endpoint::Ptr endpoint);
-	void UnregisterEndpoint(Endpoint::Ptr endpoint);
+	void RegisterEndpoint(const Endpoint::Ptr& endpoint);
+	void UnregisterEndpoint(const Endpoint::Ptr& endpoint);
 
-	void SendUnicastMessage(Endpoint::Ptr sender, Endpoint::Ptr recipient, const MessagePart& message);
-	void SendAnycastMessage(Endpoint::Ptr sender, const RequestMessage& message);
-	void SendMulticastMessage(Endpoint::Ptr sender, const RequestMessage& message);
+	void SendUnicastMessage(const Endpoint::Ptr& sender, const Endpoint::Ptr& recipient, const MessagePart& message);
+	void SendAnycastMessage(const Endpoint::Ptr& sender, const RequestMessage& message);
+	void SendMulticastMessage(const Endpoint::Ptr& sender, const RequestMessage& message);
 
 	void SendAPIMessage(const Endpoint::Ptr& sender, const Endpoint::Ptr& recipient, RequestMessage& message,
 	    function<void(const EndpointManager::Ptr&, const Endpoint::Ptr, const RequestMessage&, const ResponseMessage&, bool TimedOut)> callback, time_t timeout = 30);
@@ -65,7 +65,7 @@ public:
 	Iterator Begin(void);
 	Iterator End(void);
 
-	Endpoint::Ptr GetEndpointByIdentity(string identity) const;
+	Endpoint::Ptr GetEndpointByIdentity(const string& identity) const;
 
 	boost::signal<void (const EndpointManager::Ptr&, const Endpoint::Ptr&)> OnNewEndpoint;
 
@@ -98,8 +98,8 @@ private:
 	map<string, PendingRequest> m_Requests;
 	Timer::Ptr m_RequestTimer;
 
-	void RegisterServer(JsonRpcServer::Ptr server);
-	void UnregisterServer(JsonRpcServer::Ptr server);
+	void RegisterServer(const JsonRpcServer::Ptr& server);
+	void UnregisterServer(const JsonRpcServer::Ptr& server);
 
 	static bool RequestTimeoutLessComparer(const pair<string, PendingRequest>& a, const pair<string, PendingRequest>& b);
 	void RequestTimerHandler(void);