CLKMUX simulation

I'm using clkmux in my design. However, when I try to run simulation my project the Questa shows me an error

vsim work.clkmux
# vsim work.clkmux
# Start time: 12:14:30 on Jul 26,2024
# ** Note: (vsim-3812) Design is being optimized...
# ** Error: XXXXXXXXXXXXX/clkmux/synthesis/submodules/clkmux_altclkctrl_0.v(70): Module 'fiftyfivenm_clkctrl' is not defined.
# For instance 'clkctrl1' at path 'clkmux.altclkctrl_0.clkmux_altclkctrl_0_sub_component'
# Optimization failed
# ** Note: (vsim-12126) Error and warning message counts have been restored: Errors=4, Warnings=1.

Where can I find this fiftyfivenm_clkctrl source code?

Definitely, I can use a simple mux for simulation purposes only and use clkmux IP for the synthesis but would like to have the same code for both cases.