Can't use dead keys through xpra x11 on ubuntu linux

I'm using xpra to work on a remote ubuntu linux server from my ubuntu linux laptop, using the latest xpra x11 client and the latest xpra x11 server (installed from the xpra.org apt repository). The connection is done through openssh. I'm using a belgian keyboard (azerty, similar to french kb). The problem is the same whether I use seamless or desktop modes. However I don't have the problem when testing xpra locally on my laptop. Dead keys (circumflex accent or tilde that should appear if I press it and then another key (space for example)) don't work in any applications. Using xev, I can see the event though :

KeyPress event, serial 48, synthetic NO, window 0x3000001,
    root 0x50e, subw 0x0, time 1899047455, (114,40), root:(122,456),
    state 0x10, keycode 34 (keysym 0xfe52, dead_circumflex), same_screen YES,
    XLookupString gives 1 bytes: (5e) "^"
    XmbLookupString gives 0 bytes: 
    XFilterEvent returns: True

KeyRelease event, serial 48, synthetic NO, window 0x3000001,
    root 0x50e, subw 0x0, time 1899047456, (114,40), root:(122,456),
    state 0x10, keycode 34 (keysym 0xfe52, dead_circumflex), same_screen YES,
    XLookupString gives 1 bytes: (5e) "^"
    XFilterEvent returns: False

KeyPress event, serial 48, synthetic NO, window 0x3000001,
    root 0x50e, subw 0x0, time 1899048177, (114,40), root:(122,456),
    state 0x10, keycode 34 (keysym 0xfe52, dead_circumflex), same_screen YES,
    XLookupString gives 1 bytes: (5e) "^"
    XmbLookupString gives 0 bytes: 
    XFilterEvent returns: True

KeyPress event, serial 48, synthetic NO, window 0x3000001,
    root 0x50e, subw 0x0, time 1899048177, (114,40), root:(122,456),
    state 0x10, keycode 0 (keysym 0x5e, asciicircum), same_screen YES,
    XKeysymToKeycode returns keycode: 15
    XLookupString gives 0 bytes: 
    XmbLookupString gives 1 bytes: (5e) "^"
    XFilterEvent returns: False

KeyRelease event, serial 48, synthetic NO, window 0x3000001,
    root 0x50e, subw 0x0, time 1899048177, (114,40), root:(122,456),
    state 0x10, keycode 34 (keysym 0xfe52, dead_circumflex), same_screen YES,
    XLookupString gives 1 bytes: (5e) "^"
    XFilterEvent returns: False

I tried different input methods and different keyboard configurations in xpra but I can't get this working. Is there something I'm missing?