diff --git a/CMakeLists.txt b/CMakeLists.txt
index de3f2cf536e035103fd554aaf52e06cbf3e8ea75..7ceb1d4b7921df57de7e75012ab14082f8b8ff35 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -152,6 +152,7 @@ find_python_module(graph_tool   REQUIRED)
 find_python_module(pyopencl     REQUIRED)
 find_python_module(pyfftw       REQUIRED)
 find_python_module(gpyfft       REQUIRED)
+find_python_module(matplotlib REQUIRED)
 find_python_module(backports.weakref REQUIRED) # python-backports.weakref
 #find_python_module(backports.functools-lru-cache REQUIRED) # python-backports.functools-lru-cache
 # --- MPI ---
@@ -159,11 +160,6 @@ if(USE_MPI)
   find_package(MPI REQUIRED)
   find_python_module(mpi4py REQUIRED)
 endif()
-# --- PLOT --
-find_python_module(matplotlib)
-if(NOT matplotlib_FOUND)
-  find_python_module(Gnuplot)
-endif()
 # --- Wheel, required for a proper build/install process ---
 find_python_module(wheel REQUIRED)
 if(USE_CXX)
diff --git a/ci/docker_images/ubuntu/disco/Dockerfile b/ci/docker_images/ubuntu/disco/Dockerfile
index c206b411298f99165256c0c4d049a28ca56bfb2d..1a0ad6bfa9fcd4c634c1cff1a4d235d95a0014bf 100644
--- a/ci/docker_images/ubuntu/disco/Dockerfile
+++ b/ci/docker_images/ubuntu/disco/Dockerfile
@@ -205,8 +205,10 @@ RUN cd /tmp \
 
 # fix some python packages...
 RUN pip uninstall -y backports.weakref
-RUN apt-get install --reinstall -y python-backports.weakref
+RUN pip uninstall -y backports.functools-lru-cache
 RUN pip uninstall -y configparser
+RUN apt-get install --reinstall -y python-backports.weakref
+RUN apt-get install --reinstall -y python-backports.functools-lru-cache
 RUN apt-get install --reinstall -y python-configparser
  
 # ensure all libraries are known by the runtime linker