diff --git a/newsfragments/3731.change.md b/newsfragments/3731.change.md
new file mode 100644
index 000000000..a58de0b7f
--- /dev/null
+++ b/newsfragments/3731.change.md
@@ -0,0 +1 @@
+Use Astral's stable Python 3.15 Docker image, with `uv` pinned to 0.13.1, for the mock services.
diff --git a/src/mock_vws/_flask_server/Dockerfile b/src/mock_vws/_flask_server/Dockerfile
index 01932b28f..35b3b1f3b 100644
--- a/src/mock_vws/_flask_server/Dockerfile
+++ b/src/mock_vws/_flask_server/Dockerfile
@@ -1,11 +1,4 @@
-FROM ghcr.io/astral-sh/uv:0.13.0-trixie-slim AS base
-# The Debian base has no system certificate store for HTTPS clients.
-RUN apt-get update \
-    && apt-get install --no-install-recommends -y ca-certificates=20250419 \
-    && rm -rf /var/lib/apt/lists/*
-ENV UV_PYTHON_INSTALL_DIR=/opt/python
-ENV UV_PYTHON_BIN_DIR=/usr/local/bin
-RUN uv python install --default 3.15.0
+FROM ghcr.io/astral-sh/uv:0.13.1-python3.15-trixie-slim AS base
 # We set this pretend version as we do not have Git in our path, and we do
 # not care enough about having the version correct inside the Docker container
 # to install it.