tcltls v1.7.23 and Tcl 9

I have encountered a problem with the above extension under tcl9.0.0
After downloading https://www.tcl3d.org/bawt/download/Preview/Tcl9/tcltls-1.7.23.7z, as advertised on the "Porting extensions to Tcl 9" page on the wiki, configuring using the line
./configure --prefix=/opt/tcl9.0.0 --with-tcl=/opt/tcl9.0.0/lib
building and installing, I cannot load the extension:
     % package require tls
     version conflict for package "tcl": have 9.0.0, need 8.4
The same error also occurs if I do
     % load /opt/tcl9.0.0/lib/tcltls1.7.23/tcltls.so Tls
so I assume a problem in the .so file. I've had a quick look through the sources, but I have no confidence that I can find the appropriate change.
Please can someone help?