diff --git a/changelog.d/18272.docker b/changelog.d/18272.docker
new file mode 100644
index 0000000000..ceec619b6c
--- /dev/null
+++ b/changelog.d/18272.docker
@@ -0,0 +1 @@
+Always specify base image debian versions with a build argument.
diff --git a/docker/Dockerfile-workers b/docker/Dockerfile-workers
index 2ceb6ab67c..3dec4bba05 100644
--- a/docker/Dockerfile-workers
+++ b/docker/Dockerfile-workers
@@ -2,12 +2,13 @@
 
 ARG SYNAPSE_VERSION=latest
 ARG FROM=matrixdotorg/synapse:$SYNAPSE_VERSION
+ARG DEBIAN_VERSION=bookworm
 
 # first of all, we create a base image with an nginx which we can copy into the
 # target image. For repeated rebuilds, this is much faster than apt installing
 # each time.
 
-FROM docker.io/library/debian:bookworm-slim AS deps_base
+FROM docker.io/library/debian:${DEBIAN_VERSION}-slim AS deps_base
     RUN \
        --mount=type=cache,target=/var/cache/apt,sharing=locked \
        --mount=type=cache,target=/var/lib/apt,sharing=locked \
@@ -21,7 +22,7 @@ FROM docker.io/library/debian:bookworm-slim AS deps_base
 # which makes it much easier to copy (but we need to make sure we use an image
 # based on the same debian version as the synapse image, to make sure we get
 # the expected version of libc.
-FROM docker.io/library/redis:7-bookworm AS redis_base
+FROM docker.io/library/redis:7-${DEBIAN_VERSION} AS redis_base
 
 # now build the final image, based on the the regular Synapse docker image
 FROM $FROM
diff --git a/docker/complement/Dockerfile b/docker/complement/Dockerfile
index ce82c400eb..3e7f808cc5 100644
--- a/docker/complement/Dockerfile
+++ b/docker/complement/Dockerfile
@@ -9,6 +9,9 @@
 ARG SYNAPSE_VERSION=latest
 # This is an intermediate image, to be built locally (not pulled from a registry).
 ARG FROM=matrixdotorg/synapse-workers:$SYNAPSE_VERSION
+ARG DEBIAN_VERSION=bookworm
+
+FROM docker.io/library/postgres:13-${DEBIAN_VERSION} AS postgres_base
 
 FROM $FROM
 # First of all, we copy postgres server from the official postgres image,
@@ -20,8 +23,8 @@ FROM $FROM
 # the same debian version as Synapse's docker image (so the versions of the
 # shared libraries match).
 RUN adduser --system --uid 999 postgres --home /var/lib/postgresql
-COPY --from=docker.io/library/postgres:13-bookworm /usr/lib/postgresql /usr/lib/postgresql
-COPY --from=docker.io/library/postgres:13-bookworm /usr/share/postgresql /usr/share/postgresql
+COPY --from=postgres_base /usr/lib/postgresql /usr/lib/postgresql
+COPY --from=postgres_base /usr/share/postgresql /usr/share/postgresql
 RUN mkdir /var/run/postgresql && chown postgres /var/run/postgresql
 ENV PATH="${PATH}:/usr/lib/postgresql/13/bin"
 ENV PGDATA=/var/lib/postgresql/data