diff --git a/src/host/rootfs/etc/tmux.conf b/src/host/rootfs/etc/tmux.conf
index 1be1172..04aaca2 100644
--- a/src/host/rootfs/etc/tmux.conf
+++ b/src/host/rootfs/etc/tmux.conf
@@ -14,7 +14,7 @@ set-option -g status-left "[#S] "
 set-option -g status-right ""
 
 # The current power battery level
-set-option -ag status-right " [#(cat /sys/class/power_supply/BAT0/capacity)%%]"
+set-option -ag status-right '#(test -d /sys/class/power_supply/BAT0/capacity && printf " [%%s%%%%]" "$(cat /sys/class/power_supply/BAT0/capacity)")'
 
 # Current date and time, in case it's relevant, and has drifted
 set-option -ag status-right " [%Y-%m-%d %H:%M:%S]"