Index: guild.c
===================================================================
--- guild.c (revision 16244)
+++ guild.c (working copy)
@@ -623,6 +623,13 @@
        return 0;
    }
 
+   ARR_FIND( 0, g->max_member, i, g->member[i].class_ != tsd->status.class_ );
+   if(i)
+   {
+       clif_colormes(sd, COLOR_RED, "Your Guild already has this class");
+       return 0;
+   }
+
    tsd->guild_invite=sd->status.guild_id;
    tsd->guild_invite_account=sd->status.account_id;