diff --git a/client/CClient.cpp b/client/CClient.cpp
index 3f8ec103..4447d295 100644
--- a/client/CClient.cpp
+++ b/client/CClient.cpp
@@ -294,6 +294,10 @@ void					CClient::runSession(void*)
 				onErrorBusy();
 				break;
 			}
+			else if (memcmp(code, kMsgEUnknown, 4) == 0) {
+				onErrorUnknown();
+				break;
+			}
 			else if (memcmp(code, kMsgEBad, 4) == 0) {
 				onErrorBad();
 				break;
@@ -606,6 +610,11 @@ void					CClient::onErrorBusy()
 	log((CLOG_ERR "server already has a connected client with name \"%s\"", m_name.c_str()));
 }
 
+void					CClient::onErrorUnknown()
+{
+	log((CLOG_ERR "server refused client with name \"%s\"", m_name.c_str()));
+}
+
 void					CClient::onErrorBad()
 {
 	log((CLOG_ERR "server disconnected due to a protocol error"));
diff --git a/client/CClient.h b/client/CClient.h
index a6c0cea1..9920a45c 100644
--- a/client/CClient.h
+++ b/client/CClient.h
@@ -53,6 +53,7 @@ private:
 	void				onMouseWheel();
 	void				onErrorIncompatible();
 	void				onErrorBusy();
+	void				onErrorUnknown();
 	void				onErrorBad();
 
 private:
diff --git a/server/CServer.cpp b/server/CServer.cpp
index e7cf497f..d7c71da6 100644
--- a/server/CServer.cpp
+++ b/server/CServer.cpp
@@ -992,6 +992,11 @@ void					CServer::handshakeClient(void* vsocket)
 			log((CLOG_WARN "a client with name \"%s\" is already connected", e.getName().c_str()));
 			CProtocolUtil::writef(output.get(), kMsgEBusy);
 		}
+		catch (XUnknownClient& e) {
+			// client has unknown name
+			log((CLOG_WARN "a client with name \"%s\" is not in the map", e.getName().c_str()));
+			CProtocolUtil::writef(output.get(), kMsgEUnknown);
+		}
 		catch (XIncompatibleClient& e) {
 			// client is incompatible
 			// FIXME -- could print network address if socket had suitable method
@@ -1278,7 +1283,10 @@ CServer::CScreenInfo*	CServer::addConnection(
 		throw XDuplicateClient(name);
 	}
 
-	// FIXME -- throw if the name is not in our map
+	// name must be in our configuration
+	if (!m_config.isScreen(name)) {
+		throw XUnknownClient(name);
+	}
 
 	// save screen info
 	CScreenInfo* newScreen = new CScreenInfo(name, protocol);
diff --git a/synergy/ProtocolTypes.h b/synergy/ProtocolTypes.h
index c8194961..e06093fa 100644
--- a/synergy/ProtocolTypes.h
+++ b/synergy/ProtocolTypes.h
@@ -131,6 +131,11 @@ static const char		kMsgEIncompatible[]	= "EICV%2i%2i";
 // name provided when connecting is already in use:  primary -> secondary
 static const char		kMsgEBusy[] = "EBSY";
 
+// unknown client:  primary -> secondary
+// name provided when connecting is not in primary's screen
+// configuration map.
+static const char		kMsgEUnknown[] = "EUNK";
+
 // protocol violation:  primary -> secondary
 // primary should disconnect after sending this message.
 static const char		kMsgEBad[] = "EBAD";
diff --git a/synergy/XSynergy.cpp b/synergy/XSynergy.cpp
index d07c727c..94159f9a 100644
--- a/synergy/XSynergy.cpp
+++ b/synergy/XSynergy.cpp
@@ -55,3 +55,23 @@ CString					XDuplicateClient::getWhat() const throw()
 {
 	return "XDuplicateClient";
 }
+
+
+//
+// XUnknownClient
+//
+
+XUnknownClient::XUnknownClient(const CString& name) : m_name(name)
+{
+	// do nothing
+}
+
+const CString&			XUnknownClient::getName() const throw()
+{
+	return m_name;
+}
+
+CString					XUnknownClient::getWhat() const throw()
+{
+	return "XUnknownClient";
+}
diff --git a/synergy/XSynergy.h b/synergy/XSynergy.h
index f3dde1f6..dda1d106 100644
--- a/synergy/XSynergy.h
+++ b/synergy/XSynergy.h
@@ -50,4 +50,23 @@ private:
 	CString				m_name;
 };
 
+// client has unknown name (i.e. name is not in server's screen map)
+class XUnknownClient : public XSynergy {
+public:
+	XUnknownClient(const CString& name);
+
+	// manipulators
+
+	// accessors
+
+	virtual const CString&
+						getName() const throw();
+
+protected:
+	virtual CString		getWhat() const throw();
+
+private:
+	CString				m_name;
+};
+
 #endif