Transforming E. coli MC1061 competent cells with tetracycline resistance plasmid

I am using cloned plasmid with tetracycline resistance gene in it. I have prepared fresh competent cells E. coli MC1061, but the problem is that ideally it should not grow on tatracyline containing LB plate, but in my case it is growing. I made fresh plate, I don't understand what the problem is - is E.coli MC1061 resistant to tetracycline?

Thank you in advance