diff --git a/docker/Dockerfile_ubuntu_18.04 b/docker/Dockerfile_ubuntu_18.04
index 0b1ad37a1dd507698e7c2d4cc6ce0062f4bd32ac..930f670a3d355e1aaa084c50e3fca6812332b0da 100644
--- a/docker/Dockerfile_ubuntu_18.04
+++ b/docker/Dockerfile_ubuntu_18.04
@@ -16,6 +16,7 @@ RUN apt-get update && \
         python3-sphinx-gallery \
         python3-matplotlib \
         python3-pil \
+        python3-tk \       
         && \
     apt-get clean
 RUN apt-get install -y --no-install-recommends locales && \