diff --git a/docker/appimage/Dockerfile b/docker/appimage/Dockerfile
index 6f139a6e..153abc0b 100644
--- a/docker/appimage/Dockerfile
+++ b/docker/appimage/Dockerfile
@@ -1,118 +1,120 @@
 # Dockerfile - docker/appimage
 # Copyright (C) 2021 g10 Code GmbH
 #
 # Software engineering by Ingo Klöcker <dev@ingo-kloecker.de>
 #
 # This file is part of GnuPG.
 #
 # Gpg4win is free software; you can redistribute it and/or modify
 # it under the terms of the GNU General Public License as published by
 # the Free Software Foundation; either version 2 of the License, or
 # (at your option) any later version.
 #
 # Gpg4win is distributed in the hope that it will be useful,
 # but WITHOUT ANY WARRANTY; without even the implied warranty of
 # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 # GNU General Public License for more details.
 #
 # You should have received a copy of the GNU General Public License
 # along with this program; if not, see <https://www.gnu.org/licenses/>.
 #
 # SPDX-License-Identifier: GPL-2.0+
 
 FROM centos:7
 
 # Import the CentOS 7 package signing key after verifying its fingerprint.
 # Then add the software collections repository from the CentOS SCLo SIG and
 # import its package signing key after verifying the fingerprint.
 # Ditto for the EPEL 7 package signing key.
 RUN test $(gpg --with-colons --with-fingerprint < /etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-7 | grep ^pub: | wc -l) = 1 \
     && gpg --with-colons --with-fingerprint < /etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-7 | grep -q ^fpr:::::::::6341AB2753D78A78A7C27BB124C6A8A7F4A80EB5 \
     && rpmkeys --import /etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-7 \
     && yum -y update \
     && yum -y install \
         centos-release-scl \
     && test $(gpg --with-colons --with-fingerprint < /etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-SIG-SCLo | grep ^pub: | wc -l) = 1 \
     && gpg --with-colons --with-fingerprint < /etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-SIG-SCLo | grep -q ^fpr:::::::::C4DBD535B1FBBA14F8BA64A84EB84E71F2EE9D55 \
     && rpmkeys --import /etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-SIG-SCLo \
     && yum -y update \
     && yum -y install \
         epel-release \
     && test $(gpg --with-colons --with-fingerprint < /etc/pki/rpm-gpg/RPM-GPG-KEY-EPEL-7 | grep ^pub: | wc -l) = 1 \
     && gpg --with-colons --with-fingerprint < /etc/pki/rpm-gpg/RPM-GPG-KEY-EPEL-7 | grep -q ^fpr:::::::::91E97D7C4A5E96F17F3E888F6A2FAEA2352C64E5 \
     && rpmkeys --import /etc/pki/rpm-gpg/RPM-GPG-KEY-EPEL-7 \
     && yum -y update \
     && rm -rf /root/.gnupg
 
 RUN yum -y install \
         at-spi2-core-devel \
         automake \
+        bison \
         boost169-devel \
         bzip2 \
         bzip2-devel \
         cmake3 \
         cups-devel \
         dbus-devel \
         devtoolset-10-binutils \
         devtoolset-10-gcc \
         devtoolset-10-gcc-c++ \
         devtoolset-10-make \
         double-conversion-devel \
         egl-wayland-devel \
         file \
+        flex \
         fontconfig-devel \
         freetype-devel \
         gettext \
         git \
         gnutls-devel \
         gperf \
         gtk-update-icon-cache \
         harfbuzz-devel \
         libXrender-devel \
         libicu-devel \
         libinput-devel \
         libjpeg-devel \
         libmount-devel \
         libpng-devel \
         libusbx-devel \
         libxkbcommon-x11-devel \
         libzstd-devel \
         mesa-libEGL-devel \
         mesa-libGL-devel \
         mtdev-devel \
         openldap-devel \
         openssl11-devel \
         patch \
         pcre2-devel \
         python36-lxml \
         readline-devel \
         stow \
         systemd-devel \
         wayland-devel \
         wget \
         which \
         xcb-util-image-devel \
         xcb-util-keysyms-devel \
         xcb-util-renderutil-devel \
         xcb-util-wm-devel \
         xcb-util-devel \
         xz-devel \
         zlib-devel
 
 # download the necessary linuxdeploy AppImages and extract them because we have no fuse in the container
 RUN mkdir -p /tmp/download \
     && cd /tmp/download \
     && wget --no-verbose https://github.com/linuxdeploy/linuxdeploy/releases/download/continuous/linuxdeploy-x86_64.AppImage \
     && wget --no-verbose https://github.com/linuxdeploy/linuxdeploy-plugin-qt/releases/download/continuous/linuxdeploy-plugin-qt-x86_64.AppImage \
     && chmod +x linuxdeploy-* \
     && cd /tmp \
     && download/linuxdeploy-plugin-qt-x86_64.AppImage --appimage-extract \
     && download/linuxdeploy-x86_64.AppImage --appimage-extract \
     && rm -rf /tmp/download \
     && mkdir -p /opt \
     && mv /tmp/squashfs-root /opt/linuxdeploy
 
 # No need to copy the build scripts becuase it is available
 # in the mounted /src hierachy.
 # COPY build-appimage.sh /
 # RUN chmod +x build-appimage.sh