Setting modifier using xmodmap

I am using GNU/Linux (Devuan) with the mate desktop and with i3wm. I would like to assign mod1 to Meta_L. If I show the current assignment with $ xmodmap I get mod1 Alt_L (0x40), Meta_L (0xcd) So I tried the following: $ xmodmap -e "clear mod1" $ xmodmap xmodmap: up to 4 keys per modifier, (keycodes in parentheses): ... mod1 and then $ xmodmap -e "add mod1 = Meta_L" $ xmodmap ... mod1 Alt_L (0x40), Meta_L (0xcd) So, I am getting the old assignment back. I am not sure what is happening. Am I doing something wrong or is xmodmap or some other program ignoring / overriding my assignment?