diff --git a/.drone.yml b/.drone.yml
index f4a6800..be19c39 100644
--- a/.drone.yml
+++ b/.drone.yml
@@ -16,103 +16,49 @@ steps:
   image: debian:stretch-slim
   pull: always
   environment:
-    LANG: C.utf8
     CXX: g++-5
     CXXFLAGS: -pipe -O2
+    LANG: en_US.utf-8
   commands:
   - rm /etc/apt/apt.conf.d/docker-clean
-  - apt-get update -q
+  - alias apt-get='rm -f /var/cache/apt/archives/lock && apt-get'
   - echo "APT::Default-Release \"stretch\";" >> /etc/apt/apt.conf.d/00default_release
-  - echo "deb http://deb.debian.org/debian sid main" >> /etc/apt/sources.list.d/sid.list
   - echo "deb http://ppa.launchpad.net/ubuntu-toolchain-r/test/ubuntu xenial main" >> /etc/apt/sources.list.d/ubuntu-toolchain-r.list
+  - apt-get update -q
   - apt-get install -qy gnupg
   - gpg --keyserver hkp://keyserver.ubuntu.com --recv-keys 0x60c317803a41ba51845e371a1e9377a2ba9ef27f
   - gpg --armor --export 0x60c317803a41ba51845e371a1e9377a2ba9ef27f | apt-key add -
   - apt-get update -q
   - apt-get install -qy -t xenial g++-5
-  - apt-get install -qy cmake pkg-config
-  - apt-get install -qy libcurl4-openssl-dev libjsoncpp-dev asciidoc
-  - apt-get install -qy -t sid libcurlpp-dev
+  - apt-get install -qy cmake libpoco-dev libjsoncpp-dev asciidoc
   - rm -rf build && mkdir -p build && cd build
-  - cmake -DCMAKE_INSTALL_PREFIX=/usr ..
+  - cmake ..
   - make VERBOSE=1
   volumes:
   - name: debian-package-cache
     path: /var/cache/apt/archives
 
-- name: gcc6
+- name: gcc9
   image: debian:stretch-slim
   pull: always
   environment:
-    LANG: C.utf8
-    CXX: g++-6
+    CXX: g++-9
     CXXFLAGS: -pipe -O2
+    LANG: en_US.utf-8
   commands:
   - rm /etc/apt/apt.conf.d/docker-clean
+  - alias apt-get='rm -f /var/cache/apt/archives/lock && apt-get'
   - echo "APT::Default-Release \"stretch\";" >> /etc/apt/apt.conf.d/00default_release
-  - echo "deb http://deb.debian.org/debian sid main" >> /etc/apt/sources.list.d/sid.list
-  - apt-get update -q
-  - apt-get install -qy g++-6 cmake pkg-config
-  - apt-get install -qy libcurl4-openssl-dev libjsoncpp-dev asciidoc
-  - apt-get install -qy -t sid libcurlpp-dev
-  - rm -rf build && mkdir -p build && cd build
-  - cmake -DCMAKE_INSTALL_PREFIX=/usr ..
-  - make VERBOSE=1
-  volumes:
-  - name: debian-package-cache
-    path: /var/cache/apt/archives
-
-- name: gcc7
-  image: debian:stretch-slim
-  pull: always
-  environment:
-    LANG: C.utf8
-    CXX: g++-7
-    CXXFLAGS: -pipe -O2
-  commands:
-  - rm /etc/apt/apt.conf.d/docker-clean
-  - apt-get update -q
-  - echo "APT::Default-Release \"stretch\";" >> /etc/apt/apt.conf.d/00default_release
-  - echo "deb http://deb.debian.org/debian sid main" >> /etc/apt/sources.list.d/sid.list
   - echo "deb http://ppa.launchpad.net/ubuntu-toolchain-r/test/ubuntu xenial main" >> /etc/apt/sources.list.d/ubuntu-toolchain-r.list
+  - apt-get update -q
   - apt-get install -qy gnupg
   - gpg --keyserver hkp://keyserver.ubuntu.com --recv-keys 0x60c317803a41ba51845e371a1e9377a2ba9ef27f
   - gpg --armor --export 0x60c317803a41ba51845e371a1e9377a2ba9ef27f | apt-key add -
   - apt-get update -q
-  - apt-get install -qy -t xenial g++-7
-  - apt-get install -qy cmake pkg-config
-  - apt-get install -qy libcurl4-openssl-dev libjsoncpp-dev asciidoc
-  - apt-get install -qy -t sid libcurlpp-dev
+  - apt-get install -qy -t xenial g++-9
+  - apt-get install -qy cmake libpoco-dev libjsoncpp-dev asciidoc
   - rm -rf build && mkdir -p build && cd build
-  - cmake -DCMAKE_INSTALL_PREFIX=/usr ..
-  - make VERBOSE=1
-  volumes:
-  - name: debian-package-cache
-    path: /var/cache/apt/archives
-
-- name: gcc8
-  image: debian:stretch-slim
-  pull: always
-  environment:
-    LANG: C.utf8
-    CXX: g++-8
-    CXXFLAGS: -pipe -O2
-  commands:
-  - rm /etc/apt/apt.conf.d/docker-clean
-  - apt-get update -q
-  - echo "APT::Default-Release \"stretch\";" >> /etc/apt/apt.conf.d/00default_release
-  - echo "deb http://deb.debian.org/debian sid main" >> /etc/apt/sources.list.d/sid.list
-  - echo "deb http://ppa.launchpad.net/ubuntu-toolchain-r/test/ubuntu xenial main" >> /etc/apt/sources.list.d/ubuntu-toolchain-r.list
-  - apt-get install -qy gnupg
-  - gpg --keyserver hkp://keyserver.ubuntu.com --recv-keys 0x60c317803a41ba51845e371a1e9377a2ba9ef27f
-  - gpg --armor --export 0x60c317803a41ba51845e371a1e9377a2ba9ef27f | apt-key add -
-  - apt-get update -q
-  - apt-get install -qy -t xenial g++-8
-  - apt-get install -qy cmake pkg-config
-  - apt-get install -qy libcurl4-openssl-dev libjsoncpp-dev asciidoc
-  - apt-get install -qy -t sid libcurlpp-dev
-  - rm -rf build && mkdir -p build && cd build
-  - cmake -DCMAKE_INSTALL_PREFIX=/usr ..
+  - cmake ..
   - make VERBOSE=1
   volumes:
   - name: debian-package-cache
@@ -122,67 +68,35 @@ steps:
   image: debian:stretch-slim
   pull: always
   environment:
-    LANG: C.utf8
     CXX: clang++
     CXXFLAGS: -pipe -O2
+    LANG: en_US.utf-8
   commands:
   - rm /etc/apt/apt.conf.d/docker-clean
-  - echo "APT::Default-Release \"stretch\";" >> /etc/apt/apt.conf.d/00default_release
-  - echo "deb http://deb.debian.org/debian sid main" >> /etc/apt/sources.list.d/sid.list
+  - alias apt-get='rm -f /var/cache/apt/archives/lock && apt-get'
   - apt-get update -q
-  - apt-get install -qy clang cmake pkg-config
-  - apt-get install -qy libcurl4-openssl-dev libjsoncpp-dev asciidoc
-  - apt-get install -qy -t sid libcurlpp-dev
+  - apt-get install -qy clang cmake libpoco-dev libjsoncpp-dev asciidoc
   - rm -rf build && mkdir -p build && cd build
-  - cmake -DCMAKE_INSTALL_PREFIX=/usr ..
+  - cmake ..
   - make VERBOSE=1
   volumes:
   - name: debian-package-cache
     path: /var/cache/apt/archives
 
-- name: clang5
-  image: debian:stretch-slim
+- name: clang7
+  image: debian:buster-slim
   pull: always
   environment:
-    LANG: C.utf8
-    CXX: clang++-5.0
+    CXX: clang++
     CXXFLAGS: -pipe -O2
+    LANG: en_US.utf-8
   commands:
   - rm /etc/apt/apt.conf.d/docker-clean
-  - echo "APT::Default-Release \"stretch\";" >> /etc/apt/apt.conf.d/00default_release
-  - echo "deb http://deb.debian.org/debian sid main" >> /etc/apt/sources.list.d/sid.list
-  - echo "deb http://deb.debian.org/debian stretch-backports main" >> /etc/apt/sources.list.d/stretch.list
+  - alias apt-get='rm -f /var/cache/apt/archives/lock && apt-get'
   - apt-get update -q
-  - apt-get install -qy -t stretch-backports clang-5.0
-  - apt-get install -qy cmake pkg-config
-  - apt-get install -qy libcurl4-openssl-dev libjsoncpp-dev asciidoc
-  - apt-get install -qy -t sid libcurlpp-dev
+  - apt-get install -qy clang cmake libpoco-dev libjsoncpp-dev asciidoc
   - rm -rf build && mkdir -p build && cd build
-  - cmake -DCMAKE_INSTALL_PREFIX=/usr ..
-  - make VERBOSE=1
-  volumes:
-  - name: debian-package-cache
-    path: /var/cache/apt/archives
-
-- name: clang6
-  image: debian:stretch-slim
-  pull: always
-  environment:
-    LANG: C.utf8
-    CXX: clang++-6.0
-    CXXFLAGS: -pipe -O2
-  commands:
-  - rm /etc/apt/apt.conf.d/docker-clean
-  - echo "APT::Default-Release \"stretch\";" >> /etc/apt/apt.conf.d/00default_release
-  - echo "deb http://deb.debian.org/debian sid main" >> /etc/apt/sources.list.d/sid.list
-  - echo "deb http://deb.debian.org/debian stretch-backports main" >> /etc/apt/sources.list.d/stretch.list
-  - apt-get update -q
-  - apt-get install -qy -t stretch-backports clang-6.0
-  - apt-get install -qy cmake pkg-config
-  - apt-get install -qy libcurl4-openssl-dev libjsoncpp-dev asciidoc
-  - apt-get install -qy -t sid libcurlpp-dev
-  - rm -rf build && mkdir -p build && cd build
-  - cmake -DCMAKE_INSTALL_PREFIX=/usr ..
+  - cmake ..
   - make VERBOSE=1
   volumes:
   - name: debian-package-cache
diff --git a/README.adoc b/README.adoc
index 752c8c1..3f55b29 100644
--- a/README.adoc
+++ b/README.adoc
@@ -28,8 +28,8 @@ emerge -a dev-util/gitea2rss
 ==== Dependencies
 
 * Tested OS: Linux
-* C++ compiler (tested: https://gcc.gnu.org/[gcc] 5/6/7/8,
-  https://llvm.org/[clang] 3/5/6)
+* C++ compiler (tested: https://gcc.gnu.org/[gcc] 5/8/9,
+  https://llvm.org/[clang] 3/7)
 * https://cmake.org/[cmake] (at least: 3.6)
 * https://pocoproject.org/[POCO] (tested: 1.9 / 1.7)
 * https://github.com/open-source-parsers/jsoncpp[jsoncpp] (tested: 1.8)