diff --git a/gitlab-ci/Dockerfile b/gitlab-ci/Dockerfile
index 4a903fdbef740d6be70adfe7ec980b68c97e5e6a..c830f850e20482b5b3af84a31172d83a2e8c3027 100644
--- a/gitlab-ci/Dockerfile
+++ b/gitlab-ci/Dockerfile
@@ -12,9 +12,10 @@ ENV PATH="$PATH:$EXTLIB/bin"
 ENV PERL_CPANM_HOME="/cpanm/"
 
 RUN apt-get update; \
-    apt-get install -y --no-install-recommends gnupg wget ca-certificates; \
-    wget -O - https://sdvdebianrepo.slub-dresden.de/deb-repository/pub.gpg.key | apt-key add - ; \
-    echo "deb https://sdvdebianrepo.slub-dresden.de/deb-repository "${DEBIAN_RELEASE}" main" > /etc/apt/sources.list.d/slub.list;
+    apt-get -y upgrade; \
+    apt-get install -y --no-install-recommends gnupg wget; \
+    wget -O - http://sdvdebianrepo.slub-dresden.de/deb-repository/pub.gpg.key | apt-key add - ; \
+    echo "deb http://sdvdebianrepo.slub-dresden.de/deb-repository "${DEBIAN_RELEASE}" main" > /etc/apt/sources.list.d/slub.list;
 
 RUN if [ -f /etc/apt/sources.list ]; then \
       sed -i -e "s/^\(\(deb\|Components\).*main\( contrib\)\?\)$/\1 non-free/g" /etc/apt/sources.list; \