maim unable piping into other program

[souravdas142]

OS : Arch
WM : i3 (4.18)
Installed from : AUR / Manual Build
version : maim (5.5.3), slop(7.4)

When calling maim without any options and arguments its simply print the help page.
thats because When I tell maim to capture full screen and pipes its output to clipboard : maim | xclip -selection clipboard -t image/png maim pipes out the help page and doesn't pipe the output of image into xclip

but when i tell maim to select a area and pipes out to xclip its fine
maim -s | xclip -selection clipboard -t image/png

why maim doesn't work when its called without arguments and options to take full screen shot?

This also doesn't solve my problem for full screenshot see : 167#issuecomment-460242215