diff --git a/dockerfiles/Dockerfile.cmake-cgcore-mgx b/dockerfiles/Dockerfile.cmake-cgcore-mgx
index e06c971..fcc2d2f 100644
--- a/dockerfiles/Dockerfile.cmake-cgcore-mgx
+++ b/dockerfiles/Dockerfile.cmake-cgcore-mgx
@@ -19,18 +19,21 @@ RUN ln -snf /usr/share/zoneinfo/$TZ /etc/localtime && echo $TZ > /etc/timezone
 #==========================================
 WORKDIR /containerws
 #==========================================
-ENV MIRROR_SCRIPT=mirror.sh
-RUN curl -LO https://raw.githubusercontent.com/LIHPC-Computational-Geometry/spack_recipes/main/dockerfiles/${MIRROR_SCRIPT} &&\
-    chmod +x ${MIRROR_SCRIPT} &&\
-    ./${MIRROR_SCRIPT} build-releases ${SPACK_RECIPES_RELEASE_NUMBER}
-#==========================================
-# mgx documentation
-RUN cd /containerws/src/mgx-* &&\
-    python3 -m venv .venv &&\
+# documentation
+RUN apt update &&\
+    apt install -y graphviz sphinx pip &&\
+    apt clean &&\
+    rm -rf /var/lib/apt/lists/*
+RUN python3 -m venv .venv &&\
     source .venv/bin/activate &&\
     pip install sphinx_rtd_theme &&\
     pip install breathe &&\
     pip install -U pytest &&\
     pip install sphinx-copybutton
 #==========================================
+ENV MIRROR_SCRIPT=mirror.sh
+RUN curl -LO https://raw.githubusercontent.com/LIHPC-Computational-Geometry/spack_recipes/main/dockerfiles/${MIRROR_SCRIPT} &&\
+    chmod +x ${MIRROR_SCRIPT} &&\
+    ./${MIRROR_SCRIPT} build-releases ${SPACK_RECIPES_RELEASE_NUMBER}
+#==========================================
 ENV LD_LIBRARY_PATH=$INSTALL_DIR/mgx/lib:$INSTALL_DIR/occt-V7_1_0/lib:$INSTALL_DIR/VTK-7.1.1/lib