diff --git a/tools/linuxfs/desktop/steamdeck-desktop b/tools/linuxfs/desktop/steamdeck-desktop
index 8910ad77a..21c536b01 100644
--- a/tools/linuxfs/desktop/steamdeck-desktop
+++ b/tools/linuxfs/desktop/steamdeck-desktop
@@ -44,6 +44,28 @@ if [ -d /usr/share/fontconfig/conf.default ] && ! ls /etc/fonts/conf.d/*.conf >/
   for f in /usr/share/fontconfig/conf.default/*.conf; do ln -sf "$f" /etc/fonts/conf.d/; done
   echo "== fontconfig: linked $(ls /etc/fonts/conf.d/*.conf | wc -l) default rules"
 fi
+# Those rules map sans-serif and friends onto whatever a full distribution installs, and this
+# rootfs has one family. Naming it outright is what gives every toolkit a default font: without
+# one Gecko reports "no fonts" with families found, and draws pages with no text at all.
+if [ ! -f /etc/fonts/local.conf ]; then
+  { echo '<?xml version="1.0"?><!DOCTYPE fontconfig SYSTEM "urn:fontconfig:fonts.dtd"><fontconfig>'
+    for generic in sans-serif sans serif monospace mono cursive fantasy system-ui ui-sans-serif; do
+      case $generic in
+        serif) face="DejaVu Serif" ;;
+        mono*|ui-mono) face="DejaVu Sans Mono" ;;
+        *) face="DejaVu Sans" ;;
+      esac
+      printf '<alias binding="weak"><family>%s</family><prefer><family>%s</family></prefer></alias>\n' "$generic" "$face"
+    done
+    echo '</fontconfig>'
+  } > /etc/fonts/local.conf
+  echo "== fontconfig: wrote local.conf (DejaVu as the default family)"
+fi
+# The cache in the image was built before those rules existed; rebuild it once, and only once.
+if [ ! -f /var/cache/fontconfig/.steamdeck-built ] && command -v fc-cache >/dev/null 2>&1; then
+  fc-cache -f >/dev/null 2>&1 && touch /var/cache/fontconfig/.steamdeck-built
+  echo "== fontconfig: cache rebuilt, default sans is $(fc-match sans-serif 2>/dev/null)"
+fi
 echo "== steamdeck-desktop: labwc ($WLR_RENDERER) on $WAYLAND_DISPLAY"
 # ~/.steamdeck-desktop-debug: labwc's own debug log (views and layer surfaces mapping) too.
 DEBUG=; [ -f "$HOME/.steamdeck-desktop-debug" ] && DEBUG=-d