Extension file problem

[ed95]

Hello,
I use ST4 for coding in assembly 65816 with Merlin Assembler extension.
The problem is that after creating a new file, setting the extension to Merlin Assembler, if i close the file and reopen it the extension change to M68K-Assembly…
So i had to set it again systematicaly to the right extension…
Each time i open a file…
Any idea would be appreciate.
Regards
Eric