diff --git a/ci/docker_images/ubuntu/bionic/Dockerfile b/ci/docker_images/ubuntu/bionic/Dockerfile
index c5c854a089ab321a7f0d72dff03e89360548595d..6284b2a57bf41209663b8496e350e02c203d4f16 100644
--- a/ci/docker_images/ubuntu/bionic/Dockerfile
+++ b/ci/docker_images/ubuntu/bionic/Dockerfile
@@ -99,27 +99,11 @@ RUN cd /tmp                                     \
  && cd -                                        \
  && rm -Rf /tmp/patchelf
 
-# python graphtools
-RUN cd /tmp                                       \
- && wget https://downloads.skewed.de/graph-tool/graph-tool-2.26.tar.bz2 \
- && tar -xvjf graph-tool-2.26.tar.bz2             \
- && cd graph-tool-2.26                            \
- && ./autogen.sh                                  \
- && mkdir pycairo                                 \
- && find /usr/ -name 'pycairo.h' -exec cp {} ./pycairo/pycairo.h \; \
- && CPPFLAGS=-I. ./configure                      \
- && CPPFLAGS=-I. make                             \
- && make install                                  \
- && cd -                                          \
- && rm -Rf /tmp/graph-tool-2.26
- 
- #&& for f in $(grep -Rl '[^:]placeholders::'); do echo '%s/[^:]\zs\zeplaceholders::/std::/g | w' | vim -e $f; done; \
-    #CPPFLAGS=-I. ./configure                      \
-
-RUN echo 'deb http://apt.llvm.org/bionic/ llvm-toolchain-bionic main'     >> /etc/apt/sources.list \
+RUN  wget -O - https://apt.llvm.org/llvm-snapshot.gpg.key | apt-key add -                          \
+ && echo 'deb http://apt.llvm.org/bionic/ llvm-toolchain-bionic main'     >> /etc/apt/sources.list \
  && echo 'deb-src http://apt.llvm.org/bionic/ llvm-toolchain-bionic main' >> /etc/apt/sources.list \
- && apt-get update                                                                               \
- && apt-get install --assume-yes --allow-unauthenticated llvm-3.8 clang-3.8 libllvm3.8 libclang-3.8-dev
+ && apt-get update                                                                                 \
+ && apt-get install --assume-yes llvm-3.8 clang-3.8 libllvm3.8 libclang-3.8-dev
 
 # Intel OpenCl
 RUN cd /tmp                                                                                 \
@@ -135,7 +119,7 @@ RUN cd /tmp
 && rm -Rf /tmp/intel
 
 # Fix OpenCl ICD
-#RUN ln -s /usr/lib/x86_64-linux-gnu/libOpenCL.so.1 /usr/lib/x86_64-linux-gnu/libOpenCL.so
+RUN ln -s /usr/lib/x86_64-linux-gnu/libOpenCL.so.1 /usr/lib/x86_64-linux-gnu/libOpenCL.so
 RUN ldconfig
 
 # pyopencl
@@ -183,6 +167,21 @@ RUN cd /tmp                                      \
  && cd -                                         \
  && rm -Rf /tmp/gpyfft
 
+# python graphtools
+RUN cd /tmp                                       \
+ && wget https://downloads.skewed.de/graph-tool/graph-tool-2.26.tar.bz2 \
+ && tar -xvjf graph-tool-2.26.tar.bz2             \
+ && cd graph-tool-2.26                            \
+ && ./autogen.sh                                  \
+ && mkdir pycairo                                 \
+ && find /usr/ -name 'pycairo.h' -exec cp {} ./pycairo/pycairo.h \; \
+ && CPPFLAGS=-I. ./configure                      \
+ && CPPFLAGS=-I. make                             \
+ && make install                                  \
+ && cd -                                          \
+ && rm -Rf /tmp/graph-tool-2.26
+ 
+
 # clean cached packages
 RUN rm -rf /var/lib/apt/lists/*
 RUN rm -rf $HOME/.cache/pip/*