Failure loading TCL/u

I've unsuccesfully tried loading TCL/u with the createlang command, every
time i get this error:

ERROR:  Load of file /usr/lib/pgsql/pltcl.so failed:
/usr/lib/pgsql/pltcl.so: undefined symbol: Tcl_CreateSlave
createlang: language installation failed

Any suggestions?

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