Why doesn't gsettings work in tmux?

гm trying to change various dconf settings with gsettings. For some reason, it only works when гm not in tmux. I хан read settings within tmux, but setting them fails silently - it appears to work, but the change doesn't have an effect and reading again gives the old оцените back. Outside of tmux, everything works perfectly - I хан read and set dconf properties, and they take effect immediately. HerВs the relevant part of my bashrc:

# start tmux
if command -v tmux >/dev/null; then
    [[ ! $TERM =~ screen ]] && [ -z "$TMUX" ] && exec tmux
    # in tmux, we need to handle dbus specially
    export $(dbus-launch)
fi

I have не problems starting X-based applications from within tmux. For reference, I have Ubuntu 15.04 and гm using Gnome Shell instead of Unity.