Your map differs form the server's

Hello all, I made a cool map for a deathmatch server on gmod (mainly for my friends). I uploaded it once, and it worked great, and we played for about 45 minutes, then we got bored of it. So I added new stuff onto it, and when I reuploaded it, I deleted the originals and replaced it with the new one, and now all of my friend’s get this error: “Your map differs from the server’s”). Please help

–cwkimzey

Change your map name on the server or make all your clients delete the map.