[xmonad] windows overlap the task bar

Hello, I have been running xmonad for years on my desktop (Debian 7, then 8 and 9) and I am highly satisfied: this is the only one that prevents me to "try another thing"! On my laptop (ubuntu 18.04), the windows overlap the task bar though I use exactly the same xmonad.hs file as I do on my desktop. Could you help me ? TIA Alain  import XMonad  import XMonad.Hooks.SetWMName  import XMonad.Hooks.ManageDocks  import qualified Data.Map as M  import Graphics.X11.Xlib  import XMonad.Config.Azerty  import XMonad.Prompt  import XMonad.Prompt.Shell  import XMonad.Prompt.XMonad  import XMonad.Actions.SpawnOn  myStartUpHook :: X ()  myStartUpHook = do         spawnOn "panel" "xfce4-panel"         setWMName "LG3D"  main=do    xmonad azertyConfig      {      layoutHook=avoidStruts $ layoutHook defaultConfig      , manageHook=manageHook defaultConfig <+> manageDocks      , modMask = mod4Mask      , keys = myKeys <+> keys azertyConfig      , startupHook = myStartUpHook      } -- main=do -- xmonad { keys = myKeys <+> keys azertyConfig } --     { --     layoutHook=avoidStruts $ layoutHook defaultConfig --     , manageHook=manageHook defaultConfig <+> manageDocks --     , startupHook = setWMName "LG3D" --     } -- --  myKeys conf@(XConfig {XMonad.modMask = modm}) = M.fromList              [ ((modm, xK_F12), xmonadPrompt defaultXPConfig)              , ((modm, xK_F3 ), shellPrompt  defaultXPConfig)              ]