diff --git a/docker/Dockerfile b/docker/Dockerfile
index 2998e2fb..3caef92b 100644
--- a/docker/Dockerfile
+++ b/docker/Dockerfile
@@ -3,7 +3,7 @@ FROM ubuntu:18.04
 ENV PATH /root/.cargo/bin:$PATH
 
 RUN apt update && \
-    apt install -y --no-install-recommends \
+    DEBIAN_FRONTEND=noninteractive apt install -y --no-install-recommends \
         software-properties-common \
         gpg-agent \
         make \
@@ -26,7 +26,7 @@ RUN apt update && \
         git \
         && apt-get clean && rm -rf /var/lib/apt/lists/* /tmp/* /var/tmp/*
 
-RUN wget -O - https://apt.llvm.org/llvm-snapshot.gpg.key| apt-key add - && add-apt-repository "deb http://apt.llvm.org/bionic/ llvm-toolchain-bionic main"
+RUN wget -O - https://apt.llvm.org/llvm-snapshot.gpg.key| apt-key add - && add-apt-repository "deb http://apt.llvm.org/bionic/ llvm-toolchain-bionic-12 main"
 
 RUN apt update && \
     apt install -y --no-install-recommends \
diff --git a/docker/syntax_check.sh b/docker/syntax_check.sh
index 85f2dde9..3c991866 100755
--- a/docker/syntax_check.sh
+++ b/docker/syntax_check.sh
@@ -18,6 +18,7 @@ C_FILES=$(find . \
     -name *.c -o -name *.h -o -name *.cpp)
 
 ulimit -s 65536
+$CLANG_FORMAT_BIN --version
 $CLANG_FORMAT_BIN --verbose -style=file -n --Werror --ferror-limit=0 $C_FILES
 c_syntax_rc=$?