diff --git a/Dockerfile b/Dockerfile
index 115fd93..d04baaf 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -23,9 +23,10 @@ FROM containers.global.bsf.tools/python:3.12-slim
 
 ARG PIP_INDEX_URL=https://deps.global.bsf.tools/artifactory/api/pypi/pypi.org/simple
 
-# Configure apt to use internal Debian mirrors (trixie = Debian testing)
+# Configure apt to use internal Debian mirrors only (trixie = Debian testing)
 RUN printf 'deb https://deps.global.bsf.tools/artifactory/deb.debian.org-debian trixie main\n\
-deb https://deps.global.bsf.tools/artifactory/security.debian.org-debian-security trixie-security main\n' > /etc/apt/sources.list
+deb https://deps.global.bsf.tools/artifactory/security.debian.org-debian-security trixie-security main\n' > /etc/apt/sources.list \
+    && rm -rf /etc/apt/sources.list.d/* /var/lib/apt/lists/*
 
 # Disable proxy cache
 RUN printf 'Acquire::http::Pipeline-Depth 0;\nAcquire::http::No-Cache true;\nAcquire::BrokenProxy true;\n' > /etc/apt/apt.conf.d/99fixbadproxy