diff --git a/.github/workflows/test-and-build.yaml b/.github/workflows/test-and-build.yaml
index 46cfd28..290db10 100644
--- a/.github/workflows/test-and-build.yaml
+++ b/.github/workflows/test-and-build.yaml
@@ -14,7 +14,7 @@ jobs:
     runs-on: ubuntu-latest
     env:
       ARCH: amd64
-      DEBIAN_VERSION: buster
+      DEBIAN_VERSION: bullseye
     steps:
       - name: Checkout Repo
         uses: actions/checkout@v3
diff --git a/Dockerfile.sh b/Dockerfile.sh
index 76ae6e0..52e003c 100755
--- a/Dockerfile.sh
+++ b/Dockerfile.sh
@@ -1,7 +1,7 @@
 #!/usr/bin/env bash
 
 # @param ${ARCH}             The architecture to build. Example: amd64
-# @param ${DEBIAN_VERSION}   The debian version to build. Example: buster
+# @param ${DEBIAN_VERSION}   The debian version to build. Example: bullseye
 # @param ${ARCH_IMAGE}       What the Docker Hub Image should be tagged as [default: None]
 
 set -eux
diff --git a/Dockerfile_build b/Dockerfile_build
index 8f0606c..8574fab 100644
--- a/Dockerfile_build
+++ b/Dockerfile_build
@@ -1,4 +1,4 @@
-FROM python:3.8-buster
+FROM python:3.8-bullseye
 
 # Only works for docker CLIENT (bind mounted socket)
 COPY --from=docker:18.09.3 /usr/local/bin/docker /usr/local/bin/
diff --git a/build.yml b/build.yml
index a316274..812bce5 100644
--- a/build.yml
+++ b/build.yml
@@ -9,9 +9,9 @@ x-common-args: &common-args
 
 services:
   amd64:
-    image: pihole:${PIHOLE_DOCKER_TAG}-amd64-${DEBIAN_VERSION:-buster}
+    image: pihole:${PIHOLE_DOCKER_TAG}-amd64-${DEBIAN_VERSION:-bullseye}
     build:
       context: .
       args:
         <<: *common-args
-        PIHOLE_BASE: ghcr.io/pi-hole/docker-pi-hole-base:${DEBIAN_VERSION:-buster}-slim
\ No newline at end of file
+        PIHOLE_BASE: ghcr.io/pi-hole/docker-pi-hole-base:${DEBIAN_VERSION:-bullseye}-slim
\ No newline at end of file
diff --git a/gh-actions-test.sh b/gh-actions-test.sh
index 1bb7c5b..9d342c7 100755
--- a/gh-actions-test.sh
+++ b/gh-actions-test.sh
@@ -4,8 +4,8 @@ set -ex
 # Script ran by Github actions for tests
 #
 # @environment ${ARCH}              The architecture to build. Example: amd64.
-# @environment ${DEBIAN_VERSION}    Debian version to build. ('buster' or 'stretch').
-# @environment ${ARCH_IMAGE}        What the Docker Hub Image should be tagged as. Example: pihole/pihole:master-amd64-buster
+# @environment ${DEBIAN_VERSION}    Debian version to build. ('bullseye' or 'buster').
+# @environment ${ARCH_IMAGE}        What the Docker Hub Image should be tagged as. Example: pihole/pihole:master-amd64-bullseye
 
 # setup qemu/variables
 docker run --rm --privileged multiarch/qemu-user-static:register --reset > /dev/null
diff --git a/gh-actions-vars.sh b/gh-actions-vars.sh
index 1f10529..1959062 100755
--- a/gh-actions-vars.sh
+++ b/gh-actions-vars.sh
@@ -2,14 +2,14 @@
 set -a
 
 # @environment ${ARCH}                    The architecture to build. Defaults to 'amd64'.
-# @environment ${DEBIAN_VERSION}          Debian version to build. Defaults to 'buster'.
+# @environment ${DEBIAN_VERSION}          Debian version to build. Defaults to 'bullseye'.
 # @environment ${DOCKER_HUB_REPO}         The docker hub repo to tag images for. Defaults to 'pihole'.
 # @environment ${DOCKER_HUB_IMAGE_NAME}   The name of the resulting image. Defaults to 'pihole'.
 
 GIT_BRANCH=$(git rev-parse --abbrev-ref HEAD | sed "s/\//-/g")
 GIT_TAG=$(git describe --tags --exact-match 2> /dev/null || true)
 
-DEFAULT_DEBIAN_VERSION="buster"
+DEFAULT_DEBIAN_VERSION="bullseye"
 
 if [[ -z "${ARCH}" ]]; then
     ARCH="amd64"
diff --git a/test/conftest.py b/test/conftest.py
index 744323d..c0608b7 100644
--- a/test/conftest.py
+++ b/test/conftest.py
@@ -7,7 +7,7 @@ import testinfra
 local_host = testinfra.get_host('local://')
 check_output = local_host.check_output
 
-DEBIAN_VERSION = os.environ.get('DEBIAN_VERSION', 'buster')
+DEBIAN_VERSION = os.environ.get('DEBIAN_VERSION', 'bullseye')
 
 @pytest.fixture()
 def run_and_stream_command_output():
diff --git a/test/test_volume_data.sh b/test/test_volume_data.sh
index f4e1872..9aafefc 100755
--- a/test/test_volume_data.sh
+++ b/test/test_volume_data.sh
@@ -33,7 +33,7 @@ trap "cleanup" INT TERM EXIT
 # VOLUME TESTS
 
 # Given...
-DEBIAN_VERSION="$(DEBIAN_VERSION:-buster)"
+DEBIAN_VERSION="$(DEBIAN_VERSION:-bullseye)"
 IMAGE="${1:-pihole:v5.0-amd64}-${DEBIAN_VERSION}"   # Default is latest build test image (generic, non release/branch tag)
 VOLUMES="$(mktemp -d)"                              # A fresh volume directory
 VOL_PH="$VOLUMES/pihole"