diff --git a/.buildbot.sh b/.buildbot.sh
index e5d135d30a6c5..bf8ed031ae059 100644
--- a/.buildbot.sh
+++ b/.buildbot.sh
@@ -15,6 +15,8 @@ cmake -DCMAKE_INSTALL_PREFIX=${INST_DIR} \
     -DLLVM_ENABLE_PROJECTS="lld;clang" \
     -DCLANG_DEFAULT_PIE_ON_LINUX=OFF \
     -DBUILD_SHARED_LIBS=ON \
+    -DCMAKE_C_COMPILER=/usr/bin/clang \
+    -DCMAKE_CXX_COMPILER=/usr/bin/clang++ \
     -GNinja \
     ../llvm
 cmake --build .
diff --git a/.buildbot_dockerfile_debian b/.buildbot_dockerfile_debian
index 98613faa4c271..9d760eae901f4 100755
--- a/.buildbot_dockerfile_debian
+++ b/.buildbot_dockerfile_debian
@@ -2,9 +2,15 @@ FROM debian:bullseye
 ARG CI_UID
 RUN useradd -m -u ${CI_UID} ci
 RUN apt-get update && \
-    apt-get -y install build-essential curl cmake python3-distutils git \
+    apt-get -y install clang-13 make curl cmake python3-distutils git \
     ninja-build
 WORKDIR /ci
+RUN update-alternatives --install /usr/bin/cc cc /usr/bin/clang-13 999
+RUN update-alternatives --set cc /usr/bin/clang-13
+RUN update-alternatives --install /usr/bin/c++ c++ /usr/bin/clang++-13 999
+RUN update-alternatives --set c++ /usr/bin/clang++-13
+RUN ln -sf /usr/bin/clang-13 /usr/bin/clang
+RUN ln -sf /usr/bin/clang++-13 /usr/bin/clang++
 RUN chown ${CI_UID}:${CI_UID} .
 COPY --chown=${CI_UID}:${CI_UID} . .
 CMD sh -x .buildbot.sh