diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index 640ec286e4e712478ba35276044ea07397c944b2..56dd5b05c47529f15c8265236f73b58db5b0462c 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -19,7 +19,7 @@ cache:
 before_script:
   - export APT_CACHE_DIR=`pwd`/apt-cache && mkdir -pv $APT_CACHE_DIR
   - apt-get update -yq && apt-get -o dir::cache::archives="$APT_CACHE_DIR" install -y cmake libfftw3-dev
-  - apt-get -o dir::cache::archives="$APT_CACHE_DIR" install -y liblapack-dev python3.5 python3.5-dev python3-pip
+  - apt-get -o dir::cache::archives="$APT_CACHE_DIR" install -y liblapack-dev python3.5 python3.5-dev python3-pip python3-tk
   - pip3 install --upgrade pip
   - pip3 install scipy matplotlib nose coverage cython
   - pip3 list