diff --git a/Dockerfile b/Dockerfile
index d7fd1a3..9c7c7f5 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -7,6 +7,8 @@ FROM quay.io/pypa/manylinux2014_${TARGET_ARCH}:2024-07-15-c746fd8
 ARG BOOST_VERSION=1.85.0
 ARG HDF5_VERSION=1.14.2
 ARG NINJA_VERSION=1.12.1
+# Has to be repeated here so it's imported from the "top level" above the FROM
+ARG TARGET_ARCH
 
 ENV HDF5_VERSION=${HDF5_VERSION} \
     HDF5_DIR=/usr/local \
@@ -15,6 +17,7 @@ ENV HDF5_VERSION=${HDF5_VERSION} \
 
 RUN --mount=type=cache,target=/cache \
     if [[ "$TARGET_ARCH" == "aarch64" ]]; then NINJA_ARCH="-aarch64"; else NINJA_ARCH=""; fi \
+    && echo $NINJA_ARCH \
     && curl -fsSL -o /cache/ninja-linux.zip https://github.com/ninja-build/ninja/releases/download/v${NINJA_VERSION}/ninja-linux${NINJA_ARCH}.zip \
     && unzip /cache/ninja-linux.zip -d /usr/local/bin
 COPY install_libaec.sh libaec_cmakelists.patch install_hdf5.sh install_boost.sh /tmp/