diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index 588666c..7e33ae3 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -1,7 +1,7 @@
 include:
   local: ci/install-rkorapclient-ci.yml
 
-test-korapclient-on-stable:
+test-korapclient-on-latest:
   extends: .install-rkorapclient
   image: ubuntu:latest
   cache:
@@ -11,18 +11,8 @@
     - ccache/
     - rlib/
   script:
-    - python3 -m pip install pip -U
-    - python3 -m pip install setuptools -U
-    - python3 -m pip install pytest -U
+    - mkdir -p ~/.config/pip
+    - echo -e "[global]\nbreak-system-packages = true" >> ~/.config/pip/pip.conf 
     - python3 -m pip install .
     - python3 -m pytest -v
 
-
-test-korapclient-on-rolling:
-  extends: .install-rkorapclient
-  image: ubuntu:rolling
-  script:
-    - python3 -m pip install pip -U --break-system-packages
-    - python3 -m pip install pytest -U --break-system-packages
-    - python3 -m pip install . --break-system-packages
-    - python3 -m pytest -v
diff --git a/Readme.md b/Readme.md
index e4698c9..ec07d1d 100644
--- a/Readme.md
+++ b/Readme.md
@@ -14,23 +14,27 @@
 via [rpy2](https://rpy2.github.io/). The latter also automatically translates between R data frames (or [tibbles](https://tibble.tidyverse.org/)) and [pandas DataFrames](https://pandas.pydata.org/docs/reference/api/pandas.DataFrame.html). 
 
 ## Installation
+
 #### 1. Install latest R version for your OS, following the instructions from [CRAN](https://cran.r-project.org/bin/)
 
 #### Linux only: Install system dependencies
 
 ```shell script
 #### Debian / Ubuntu
-sudo apt install r-base-dev r-cran-rcpp r-cran-cpp11 libcurl4-gnutls-dev libxml2-dev libsodium-dev libsecret-1-dev libfontconfig1-dev libssl-dev libv8-dev python3-dev python3-pip python3-rpy2 python3-pandas python3-pytest
+sudo apt install r-base-dev r-cran-rcpp r-cran-cpp11 libcurl4-gnutls-dev libxml2-dev libsodium-dev libsecret-1-dev libfontconfig1-dev libssl-dev libv8-dev python3-dev python3-pip python3-rpy2 python3-pandas python3-pytest libdeflate-dev r-cran-rcpparmadillo
 
 #### Fedora / CentOS / RHEL
 sudo yum install -y R R-devel libcurl-devel openssl-devel libxml2-devel libsodium-devel python3-pandas
 ```
 
 #### 2. Install the RKorAPClient package
+
 Start R and run:
+
 ```R
 install.packages('RKorAPClient', repos='https://cloud.r-project.org/')
 ```
+
 or install RKorAPClient from the package installation menu entry.
 
 #### 3. Install the Python package
@@ -43,6 +47,7 @@
 ```
 
 On Windows:
+
 ```shell script
 # py -m pip install pip -U
 py -m pip install KorAPClient -U
diff --git a/ci/Makevars b/ci/Makevars
index 1292033..208b7f7 100644
--- a/ci/Makevars
+++ b/ci/Makevars
@@ -2,8 +2,8 @@
 CXX17=$(CCACHE) g++$(VER)
 CCACHE=ccache
 #CCACHE=
-CC=$(CCACHE) gcc$(VER)
-CXX=$(CCACHE) g++$(VER)
+CC=$(CCACHE) gcc$(VER) -Wno-error=format-security
+CXX=$(CCACHE) g++$(VER) -Wno-error=format-security
 CXX11=$(CCACHE) g++$(VER)
 CXX14=$(CCACHE) g++$(VER)
 CXX17=$(CCACHE) g++$(VER)
diff --git a/ci/install-rkorapclient-ci.yml b/ci/install-rkorapclient-ci.yml
index 3fc7d87..23f26eb 100644
--- a/ci/install-rkorapclient-ci.yml
+++ b/ci/install-rkorapclient-ci.yml
@@ -33,12 +33,15 @@
     - echo "R_LIBS='$R_LIBS_USER'" > .Renviron
     - echo "MAKEFLAGS=-j$(nproc)" >> ~/.R/Makevars
     - echo "MAKE=make -j$(nproc)" >> ~/.R/Makevars
+    - echo "CFLAGS+=-Wno-error=format-security" >> ~/.R/Makevars
+    - echo "CCFLAGS+=-Wformat=0" >> ~/.R/Makevars
     - apt-get update
-    - apt-get install -y -o dir::cache::archives="$APT_CACHE_DIR" --no-install-recommends software-properties-common dirmngr ccache wget python3-pip
+    - apt-get install -y -o dir::cache::archives="$APT_CACHE_DIR" --no-install-recommends software-properties-common dirmngr ccache wget python3-pip libdeflate-dev
     - wget -qO- https://cloud.r-project.org/bin/linux/ubuntu/marutter_pubkey.asc | tee -a /etc/apt/trusted.gpg.d/cran_ubuntu_key.asc
     - add-apt-repository "deb https://cloud.r-project.org/bin/linux/ubuntu $(lsb_release -cs)-cran40/"
-     # - add-apt-repository ppa:c2d4u.team/c2d4u4.0+
+    - add-apt-repository -y ppa:c2d4u.team/c2d4u4.0+
     - grep -E "sudo apt.* install" Readme.md | sed -e 's/.*sudo apt.* install/apt-get install --no-install-recommends -o dir::cache::archives="$APT_CACHE_DIR" -y libharfbuzz-dev libfribidi-dev /g' | sh
+    - apt-get install -y -o dir::cache::archives="$APT_CACHE_DIR" r-cran-tidyverse
     - ln -s $(which ccache) /usr/local/sbin/gcc
     - ln -s $(which ccache) /usr/local/sbin/g++
     - end_section install_linux_packages