diff --git a/TESTING.md b/TESTING.md
index d57c5ec..68b366d 100644
--- a/TESTING.md
+++ b/TESTING.md
@@ -5,7 +5,7 @@
 To test a particular devcontainer feature, say, `lazygit`:
 
 ```bash
-devcontainer features test -f lazygit -i mcr.microsoft.com/devcontainers/base:ubuntu-24.04 .
+devcontainer features test -f lazygit -i mcr.microsoft.com/devcontainers/base:ubuntu -p .
 ```
 
 - `--skip-scenarios` ... tests only the `test.sh` test case, but no scenario tests.
diff --git a/src/pull-through-cache-registry/NOTES.md b/src/pull-through-cache-registry/NOTES.md
index ae5db03..4fa1116 100644
--- a/src/pull-through-cache-registry/NOTES.md
+++ b/src/pull-through-cache-registry/NOTES.md
@@ -10,6 +10,12 @@ In the best tradition of
 [dogfooding](https://en.wikipedia.org/wiki/Eating_your_own_dog_food) we use this
 feature to develop our features.
 
+## Important
+
+- this feature depends on `ghcr.io/devcontainers/features/docker-in-docker:3`.
+- at this time, it needs to set the docker-in-docker configuration parameter
+  `moby` to `false` in order to work on Debian 13 as well as Ubuntu 26.04.
+
 ## OS Support
 
 As this feature relies on the [Docker-in-Docker
diff --git a/src/pull-through-cache-registry/devcontainer-feature.json b/src/pull-through-cache-registry/devcontainer-feature.json
index 19fee0d..bbcd7a4 100644
--- a/src/pull-through-cache-registry/devcontainer-feature.json
+++ b/src/pull-through-cache-registry/devcontainer-feature.json
@@ -42,6 +42,8 @@
     ],
     "postCreateCommand": "/usr/local/bin/registry-pull-through-cache",
     "dependsOn": {
-        "ghcr.io/devcontainers/features/docker-in-docker:2": {}
+        "ghcr.io/devcontainers/features/docker-in-docker:3": {
+            "moby": false
+        }
     }
 }
diff --git a/src/pull-through-cache-registry/install.sh b/src/pull-through-cache-registry/install.sh
index 9b2450b..4b582d0 100755
--- a/src/pull-through-cache-registry/install.sh
+++ b/src/pull-through-cache-registry/install.sh
@@ -14,7 +14,10 @@ WAIT=${WAIT:-30}
 echo "installing feature registry-pull-through-cache"
 
 cat <<EOF >"${REGISTRYDEPLOYSCRIPT_PATH}"
-PROXY_REMOTE_URL=${PROXY_REMOTE_URL}
+#!/bin/bash
+set -eu
+
+PROXY_REMOTE_URL="${PROXY_REMOTE_URL}"
 PORT="${PORT}"
 TTL="${TTL}"
 REGISTRY_NAME="${REGISTRY_NAME}"
@@ -23,8 +26,8 @@ timeout=${WAIT}
 echo "waiting up to ${WAIT}s for Docker daemon to become responsive..."
 while ! docker ps >/dev/null 2>&1; do
     sleep 1
-    timeout=$((timeout-1))
-    if [ "$timeout" -le 0 ]; then
+    timeout=\$((timeout-1))
+    if [ "\$timeout" -le 0 ]; then
         echo "Docker did not become responsive, aborting"
         exit 1
     fi
diff --git a/test/pull-through-cache-registry/scenarios.json b/test/pull-through-cache-registry/scenarios.json
index b962093..26196b7 100644
--- a/test/pull-through-cache-registry/scenarios.json
+++ b/test/pull-through-cache-registry/scenarios.json
@@ -1,6 +1,6 @@
 {
     "9999": {
-        "image": "mcr.microsoft.com/devcontainers/base:ubuntu-24.04",
+        "image": "mcr.microsoft.com/devcontainers/base:ubuntu",
         "features": {
             "pull-through-cache-registry": {
                 "port": "9999"
@@ -8,7 +8,7 @@
         }
     },
     "quay.io": {
-        "image": "mcr.microsoft.com/devcontainers/base:ubuntu-24.04",
+        "image": "mcr.microsoft.com/devcontainers/base:ubuntu",
         "features": {
             "pull-through-cache-registry": {
                 "proxy-remote-url": "https://quay.io"