diff --git a/builder/dockerfile.ubuntu_focal.build b/builder/dockerfile.ubuntu_focal.build
index 0645c0d..33fc74a 100644
--- a/builder/dockerfile.ubuntu_focal.build
+++ b/builder/dockerfile.ubuntu_focal.build
@@ -22,9 +22,8 @@ RUN cd /tmp/libwebp-1.0.2 && \
     ./configure --enable-static --disable-shared && \
     make && make install
 
-RUN apt-get update && apt-get install -y cmake nasm gcc
-RUN git clone https://github.com/libjpeg-turbo/libjpeg-turbo.git
-RUN export MAKEFLAGS=-j`nproc`; export CFLAGS="-fno-semantic-interposition -fpic -flto"; cd libjpeg-turbo && cmake -DCMAKE_INSTALL_PREFIX=/usr/ -G"Unix Makefiles" && make && make install
+COPY builder/scripts /scripts
+RUN /scripts/build-libjpeg-turbo
 
 RUN useradd -m docker && echo "docker:docker" | chpasswd && adduser docker sudo
 
diff --git a/builder/scripts/build-libjpeg-turbo b/builder/scripts/build-libjpeg-turbo
new file mode 100755
index 0000000..dc5bff8
--- /dev/null
+++ b/builder/scripts/build-libjpeg-turbo
@@ -0,0 +1,30 @@
+#!/usr/bin/env bash
+
+set -euo pipefail
+
+build_and_install() {
+  export MAKEFLAGS=-j`nproc`
+  export CFLAGS="-fno-semantic-interposition -fpic -flto"
+  cmake -DCMAKE_INSTALL_PREFIX=/usr/local -G"Unix Makefiles"
+  make
+  make install
+}
+
+install_build_dependencies() {
+  apt-get update
+  apt-get install -y cmake gcc
+  ensure_libjpeg_is_fast
+}
+
+ensure_libjpeg_is_fast() {
+  apt-get install -y nasm
+}
+
+prepare_libjpeg_source() {
+  git clone --depth=1 https://github.com/libjpeg-turbo/libjpeg-turbo.git
+  cd libjpeg-turbo
+}
+
+install_build_dependencies
+prepare_libjpeg_source
+build_and_install