diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index b0adaaead..387419ccc 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -15,7 +15,7 @@ jobs:
       - name: Set up Go 1.x
         uses: actions/setup-go@v2
         with:
-          go-version: ^1.20
+          go-version: ^1.21
 
       - name: Check out code
         uses: actions/checkout@v2
diff --git a/Dockerfile b/Dockerfile
index b3c6b9388..18ac412f8 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -1,47 +1,23 @@
-ARG GOLANG_VERSION=1.20.8
-FROM golang:${GOLANG_VERSION}-bullseye as builder
+ARG GOLANG_VERSION=1.21.4
+FROM golang:${GOLANG_VERSION}-bookworm as builder
 
 ARG VIPS_VERSION=8.14.5
-ARG CGIF_VERSION=0.3.0
-ARG LIBSPNG_VERSION=0.7.3
 ARG TARGETARCH
 
 ENV PKG_CONFIG_PATH=/usr/local/lib/pkgconfig
 
-# libaom3 is in Debian bullseye-backports
-RUN echo 'deb http://deb.debian.org/debian bullseye-backports main' > /etc/apt/sources.list.d/backports.list
-
 # Installs libvips + required libraries
 RUN DEBIAN_FRONTEND=noninteractive \
   apt-get update && \
   apt-get install --no-install-recommends -y \
   ca-certificates \
   automake build-essential curl \
-  python3-pip ninja-build pkg-config \
+  meson ninja-build pkg-config \
   gobject-introspection gtk-doc-tools libglib2.0-dev libjpeg62-turbo-dev libpng-dev \
-  libwebp-dev libtiff5-dev libexif-dev libxml2-dev libpoppler-glib-dev \
+  libwebp-dev libtiff-dev libexif-dev libxml2-dev libpoppler-glib-dev \
   swig libpango1.0-dev libmatio-dev libopenslide-dev libcfitsio-dev libopenjp2-7-dev liblcms2-dev \
-  libgsf-1-dev fftw3-dev liborc-0.4-dev librsvg2-dev libimagequant-dev libaom-dev/bullseye-backports libheif-dev && \
-  pip3 install meson && \
-  cd /tmp && \
-    curl -fsSLO https://github.com/dloebl/cgif/archive/refs/tags/V${CGIF_VERSION}.tar.gz && \
-    tar xf V${CGIF_VERSION}.tar.gz && \
-    cd cgif-${CGIF_VERSION} && \
-    meson build --prefix=/usr/local --libdir=/usr/local/lib --buildtype=release && \
-    cd build && \
-    ninja && \
-    ninja install && \
-  cd /tmp && \
-    curl -fsSLO https://github.com/randy408/libspng/archive/refs/tags/v${LIBSPNG_VERSION}.tar.gz && \
-    tar xf v${LIBSPNG_VERSION}.tar.gz && \
-    cd libspng-${LIBSPNG_VERSION} && \
-    meson setup _build \
-      --buildtype=release \
-      --strip \
-      --prefix=/usr/local \
-      --libdir=lib && \
-    ninja -C _build && \
-    ninja -C _build install && \
+  libgsf-1-dev libfftw3-dev liborc-0.4-dev librsvg2-dev libimagequant-dev libaom-dev \
+  libheif-dev libspng-dev libcgif-dev && \
   cd /tmp && \
     curl -fsSLO https://github.com/libvips/libvips/releases/download/v${VIPS_VERSION}/vips-${VIPS_VERSION}.tar.xz && \
     tar xf vips-${VIPS_VERSION}.tar.xz && \
@@ -57,7 +33,6 @@ RUN DEBIAN_FRONTEND=noninteractive \
     ninja -C _build && \
     ninja -C _build install && \
   ldconfig && \
-  rm -rf /usr/local/lib/python* && \
   rm -rf /usr/local/lib/libvips-cpp.* && \
   rm -rf /usr/local/lib/*.a && \
   rm -rf /usr/local/lib/*.la
@@ -74,21 +49,21 @@ COPY . .
 RUN if [ "$TARGETARCH" = "amd64" ]; then go test ./...; fi
 RUN go build -o ${GOPATH}/bin/imagor ./cmd/imagor/main.go
 
-FROM debian:bullseye-slim
+FROM debian:bookworm-slim
 LABEL maintainer="adrian@cshum.com"
 
 COPY --from=builder /usr/local/lib /usr/local/lib
 COPY --from=builder /etc/ssl/certs /etc/ssl/certs
-COPY --from=builder /etc/apt/sources.list.d/backports.list /etc/apt/sources.list.d/backports.list
 
 # Install runtime dependencies
 RUN DEBIAN_FRONTEND=noninteractive \
   apt-get update && \
   apt-get install --no-install-recommends -y \
-  procps libglib2.0-0 libjpeg62-turbo libpng16-16 libopenexr25 \
-  libwebp6 libwebpmux3 libwebpdemux2 libtiff5 libexif12 libxml2 libpoppler-glib8 \
+  procps libglib2.0-0 libjpeg62-turbo libpng16-16 libopenexr-3-1-30 \
+  libwebp7 libwebpmux3 libwebpdemux2 libtiff6 libexif12 libxml2 libpoppler-glib8 \
   libpango1.0-0 libmatio11 libopenslide0 libopenjp2-7 libjemalloc2 \
-  libgsf-1-114 fftw3 liborc-0.4-0 librsvg2-2 libcfitsio9 libimagequant0 libaom3 libheif1 && \
+  libgsf-1-114 libfftw3-bin liborc-0.4-0 librsvg2-2 libcfitsio10 libimagequant0 libaom3 libheif1 \
+  libspng0 libcgif0 && \
   ln -s /usr/lib/$(uname -m)-linux-gnu/libjemalloc.so.2 /usr/local/lib/libjemalloc.so && \
   apt-get autoremove -y && \
   apt-get autoclean && \