diff --git a/debian/salsa-ci.yml b/debian/salsa-ci.yml
index 43bf300..8e6803b 100644
--- a/debian/salsa-ci.yml
+++ b/debian/salsa-ci.yml
@@ -26,7 +26,7 @@ shellcheck:
   script:
     - apt-get update && apt-get upgrade -y
     - apt-get install -y shellcheck
-    - shellcheck -e SC1090,SC1091,SC2086,SC2154 -s dash $(find rootfs/etc/initramfs-tools -type f -executable  | xargs grep -l '^#!/bin/sh')
+    - shellcheck -e SC1090,SC1091,SC2086 -s dash $(find rootfs/etc/initramfs-tools -type f -executable  | xargs grep -l '^#!/bin/sh')
 
 build yamls:
   stage: build
diff --git a/rootfs/etc/initramfs-tools/scripts/local-bottom/rpi-resizerootfs b/rootfs/etc/initramfs-tools/scripts/local-bottom/rpi-resizerootfs
index 09bf36f..a426a3f 100755
--- a/rootfs/etc/initramfs-tools/scripts/local-bottom/rpi-resizerootfs
+++ b/rootfs/etc/initramfs-tools/scripts/local-bottom/rpi-resizerootfs
@@ -33,8 +33,8 @@ fi
 
 log_begin_msg "$0 resizing $ROOT"
 
-# Unmount for safety
-umount "${rootmnt}"
+# Unmount for safety; fail if unset or empty (shellcheck SC2154)
+umount "${rootmnt:?}"
 
 # Expand the partition size to fill the entire device
 parted -s $rootdev resizepart $rootpart_nr 100%