build failing: no member named 'to_uri' in 'libbitcoin::system::config::endpoint'

[MarnixCroes]

src/zmq/socket.cpp:198:33: error: no member named 'to_uri' in 'libbitcoin::system::config::endpoint'
    if (zmq_bind(self_, address.to_uri().c_str()) == zmq_fail)
                        ~~~~~~~ ^
src/zmq/socket.cpp:206:36: error: no member named 'to_uri' in 'libbitcoin::system::config::endpoint'
    if (zmq_connect(self_, address.to_uri().c_str()) == zmq_fail)
                           ~~~~~~~ ^
2 errors generated.
make: *** [Makefile:1088: src/zmq/libbitcoin_protocol_la-socket.lo] Error 1

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