diff --git a/comm_tcp_socket_client.h b/comm_tcp_socket_client.h
index 5f457ab..ada088d 100644
--- a/comm_tcp_socket_client.h
+++ b/comm_tcp_socket_client.h
@@ -33,7 +33,7 @@ public:
 	comm_tcp_socket_client(const std::string & host, const int port);
 	virtual ~comm_tcp_socket_client();
 
-	std::string get_identifier() const override { host + format(":%d", port) + " (client)"; }
+	std::string get_identifier() const override { return host + format(":%d", port) + " (client)"; }
 
 	bool    is_connected() override;
 
diff --git a/comm_tcp_socket_server.h b/comm_tcp_socket_server.h
index fa4a98c..2b29b6c 100644
--- a/comm_tcp_socket_server.h
+++ b/comm_tcp_socket_server.h
@@ -32,7 +32,7 @@ public:
 	comm_tcp_socket_server(const int port);
 	virtual ~comm_tcp_socket_server();
 
-	std::string get_identifier() const override { format(":%d", port) + " (server)"; }
+	std::string get_identifier() const override { return format(":%d", port) + " (server)"; }
 
 	bool    is_connected() override;