diff --git a/README.md b/README.md
index 07fcaed..bdf4901 100644
--- a/README.md
+++ b/README.md
@@ -640,7 +640,7 @@ Then you can proceed with `make build` command.
 <a name="ubuntu_2604_rust"></a>
 ### Ubuntu 26.04 LTS: Rust Coreutils and sudo-rs
 
-Ubuntu 26.04 LTS "Resolute Ringtail" introduced two significant changes compared to earlier Ubuntu releases:
+Ubuntu 26.04 LTS introduced two significant changes compared to earlier Ubuntu releases:
 
 1. **Rust Coreutils (`uutils-coreutils`)** — Ubuntu 26.04 ships [uutils-coreutils](https://github.com/uutils/coreutils), a Rust-based reimplementation of the GNU Core Utilities (`ls`, `cp`, `mv`, `cat`, etc.), as the default `coreutils` package. This replaces the traditional [GNU Coreutils](https://www.gnu.org/software/coreutils/).
 
@@ -682,7 +682,7 @@ docker build --build-arg BASE_IMAGE=ubuntu:26.04 --build-arg INSTALL_GNU_COREUTI
 Alternatively, you can install GNU Coreutils in your own Dockerfile that derives from a 26.04-based baseimage:
 
 ```Dockerfile
-FROM phusion/baseimage:resolute-1.0.0
+FROM phusion/baseimage:<ubuntu-26.04-version>
 
 # Replace uutils-coreutils with GNU Coreutils and sudo-rs with traditional sudo.
 RUN apt-get update && \
diff --git a/image/prepare.sh b/image/prepare.sh
index 7af12a0..966b7c3 100755
--- a/image/prepare.sh
+++ b/image/prepare.sh
@@ -91,6 +91,18 @@ if grep -E '^ID=' /etc/os-release | grep -q ubuntu; then
         fi
         exit 1
       fi
+      # Verify that GNU coreutils are now the active implementation on PATH.
+      # Some packages may install binaries under a non-default path and rely on
+      # update-alternatives; if so the replacement has not taken effect.
+      if ! ls --version 2>&1 | grep -qi 'gnu coreutils'; then
+        echo "*** ERROR: coreutils-gnu was installed but GNU coreutils are not active on PATH." >&2
+        echo "*** 'ls --version' does not report 'GNU coreutils'." >&2
+        echo "*** The package may place binaries outside the default PATH or require" >&2
+        echo "*** manual update-alternatives configuration. Check Ubuntu 26.04 packaging." >&2
+        exit 1
+      fi
+      LS_VER=$(ls --version | head -1)
+      echo "*** GNU Coreutils are active ($LS_VER)."
     else
       echo "*** Ubuntu 26.04 detected: using default uutils-coreutils (Rust) and sudo-rs (Rust)."
       echo "*** Set INSTALL_GNU_COREUTILS=1 at build time to use GNU Coreutils and traditional sudo instead."