diff --git a/CHANGELOG.md b/CHANGELOG.md
index 66a1f58..da6e720 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -8,6 +8,7 @@ one per merged pull request.
 ## 2.11.0 - 2026-10-01
 
 - `5da1833` **feat: "Start Steam silently" sub-option: under the SteamOS conversion (`silent`, opt-in now: it was always on before; an existing one is moved from its systemd unit to the autostart entry by the "update") and under Gaming on NVIDIA (`nvsilent`, opt-in, not together with Big Picture); the SteamOS one is called "Start Steam silently in desktop mode" and is always shown, also on a Steam Machine; it is Steam's own autostart entry (`~/.config/autostart/steam.desktop`), so Steam's setting "Run Steam when my computer starts" follows it**
+- **fix: the Steam Machine's serial number step no longer fails inside the ISO's installer (`/sys` is read-only in its chroot; the tmpfiles.d file applies at the next boot anyway), which made `machine` report an error and the install log end with `exit: 1`**
 - **feat: `STEAMIFY_NO_DOWNLOAD` (the ISO's `steamify.nodownload` kernel parameter): the installed system's first login runs the Steamify bundle of the ISO instead of downloading the newest release (to test an unreleased Steamify)**
 - **fix: the SteamOS theme no longer leaves a blank Discover pin in the taskbar (Plasma's default taskbar pins Discover, which CachyOS doesn't install); the taskbar gets CachyOS's own pins (System Settings, files, browser), also on the ISO's first login**
 - **feat: "Steam Deck/Machine icons" (`glyphs`) is a sub-option of the SteamOS conversion, like "Start Steam silently in desktop mode": it only changes gaming mode**
diff --git a/lib/steam-machine.sh b/lib/steam-machine.sh
index ceb6ed7..77833a8 100644
--- a/lib/steam-machine.sh
+++ b/lib/steam-machine.sh
@@ -407,9 +407,12 @@ wifi_backend_disable() {
 
 serial_enable() {
     printf '%s\n' "# Written by Steamify: Steam shows the serial number, like on SteamOS." \
-        'z /sys/class/dmi/id/product_serial 0444 - - -' | sudo tee "$SERIAL_TMPFILES" > /dev/null &&
-        sudo systemd-tmpfiles --create "$SERIAL_TMPFILES" ||
+        'z /sys/class/dmi/id/product_serial 0444 - - -' | sudo tee "$SERIAL_TMPFILES" > /dev/null ||
         { err "Making the serial number readable for Steam failed."; return 1; }
+    # The file applies at every boot; now too, unless /sys is read-only (the ISO's installer runs in a chroot).
+    sudo systemd-tmpfiles --create "$SERIAL_TMPFILES" 2>/dev/null ||
+        info "The serial number becomes readable for Steam at the next boot."
+    return 0
 }
 
 serial_disable() {