FOSS gamedev and creative worlds

Always if i want to start a mod there is this error:
ERROR: Failed to enable mod "moretrees-master" as it contains disallowed charakters. Only Characters. [a-z0-9] are allowed.

What have i to do that the mods run?
It is so with all mods!!

Thank You for your answer

You have to remove the " -master" from the mod name.
It this case rename "moretrees-master" to "moretrees" and it should work.

http://dev.minetest.net/Installing_Mods

What if there isn't any bad characters in the name?
eg. Streets

Cactusman04 wrote:Streets

it must be "streets" because [a-z0-9] are allowed