The gzip.html example from the website doesn't compile

[yurivict]

Example from the bottom of this page: https://www.boost.org/doc/libs/1_69_0/libs/iostreams/doc/classes/gzip.html fails to compile:

$ c++ -o gunzip gunzip.cpp -I /usr/local/include/
gunzip.cpp:12:5: error: no template named 'filtering_streambuf'; did you mean 'boost::iostreams::filtering_streambuf'?
    filtering_streambuf<input> in;
    ^~~~~~~~~~~~~~~~~~~
    boost::iostreams::filtering_streambuf
/usr/local/include/boost/iostreams/filtering_streambuf.hpp:60:41: note: 'boost::iostreams::filtering_streambuf' declared here
BOOST_IOSTREAMS_DEFINE_FILTER_STREAMBUF(filtering_streambuf, boost::iostreams::chain, char)
                                        ^

The example looks like it should produce an executable.

boost-libs-1.69.0_1 on FreeBSD 11.2