diff --git a/docker/build_scripts/build-cpython.sh b/docker/build_scripts/build-cpython.sh
index eea89e22..8a5854d6 100755
--- a/docker/build_scripts/build-cpython.sh
+++ b/docker/build_scripts/build-cpython.sh
@@ -24,11 +24,11 @@ function pyver_dist_dir {
 }
 
 CPYTHON_DIST_DIR=$(pyver_dist_dir ${CPYTHON_VERSION})
-fetch_source Python-${CPYTHON_VERSION}.tgz ${CPYTHON_DOWNLOAD_URL}/${CPYTHON_DIST_DIR}
-fetch_source Python-${CPYTHON_VERSION}.tgz.asc ${CPYTHON_DOWNLOAD_URL}/${CPYTHON_DIST_DIR}
+fetch_source Python-${CPYTHON_VERSION}.tar.xz ${CPYTHON_DOWNLOAD_URL}/${CPYTHON_DIST_DIR}
+fetch_source Python-${CPYTHON_VERSION}.tar.xz.asc ${CPYTHON_DOWNLOAD_URL}/${CPYTHON_DIST_DIR}
 gpg --import ${MY_DIR}/cpython-pubkeys.txt
-gpg --verify Python-${CPYTHON_VERSION}.tgz.asc
-tar -xzf Python-${CPYTHON_VERSION}.tgz
+gpg --verify Python-${CPYTHON_VERSION}.tar.xz.asc
+tar -xJf Python-${CPYTHON_VERSION}.tar.xz
 pushd Python-${CPYTHON_VERSION}
 PREFIX="/opt/_internal/cpython-${CPYTHON_VERSION}"
 mkdir -p ${PREFIX}/lib
diff --git a/tools/update_native_dependencies.py b/tools/update_native_dependencies.py
index 5c261e46..aee89070 100644
--- a/tools/update_native_dependencies.py
+++ b/tools/update_native_dependencies.py
@@ -40,7 +40,7 @@ def _update_cpython(dry_run):
         if latest_version > current_version:
             root = f"Python-{latest_version}"
             url = f"https://www.python.org/ftp/python/{latest_version.major}.{latest_version.minor}.{latest_version.micro}"
-            _sha256(f"{url}/{root}.tgz")
+            _sha256(f"{url}/{root}.tar.xz")
             lines[i] = lines[i].replace(match["version"], str(latest_version))
             message = f"Bump CPython {current_version} → {latest_version}"
             print(message)