diff --git a/utils/build-script b/utils/build-script
index d5be8b1b24d8d..20f036bb49ff9 100755
--- a/utils/build-script
+++ b/utils/build-script
@@ -995,12 +995,12 @@ To build with AddressSanitizer:
 
   [~/src/s]$ ./swift/utils/build-script --preset=asan
 
-To build a root for Xcode XYZ, '/tmp/xcode-xyz-root.tar.gz':
+To build a root for Xcode XYZ, '/tmp/xcode-xyz-root.tar.xz':
 
   [~/src/s]$ ./swift/utils/build-script --preset=buildbot_BNI_internal_XYZ \\
       install_destdir="/tmp/install"
       install_symroot="/tmp/symroot"
-      installable_package="/tmp/xcode-xyz-root.tar.gz"
+      installable_package="/tmp/xcode-xyz-root.tar.xz"
 
 If you have your own favorite set of options, you can create your own, local,
 preset.  For example, let's create a preset called 'ds' (which stands for
diff --git a/utils/build-script-impl b/utils/build-script-impl
index 2d6f1355b16ef..3c674aa5fa1c5 100755
--- a/utils/build-script-impl
+++ b/utils/build-script-impl
@@ -2775,15 +2775,15 @@ function build_and_test_installable_package() {
           # host_install_destdir contains the toolchain prefix.
           # We want to create the package in host_install_destdir_nonprefixed.
           with_pushd "${host_install_destdir}" \
-              call tar -c -z -f "${package_for_host}" "${TOOLCHAIN_PREFIX/#\/}"
+              call tar -c -J -f "${package_for_host}" "${TOOLCHAIN_PREFIX/#\/}"
         else
             # tar on OS X doesn't support --owner/--group.
             if [[ "$(uname -s)" == "Darwin" ]] ; then
                 with_pushd "${host_install_destdir}" \
-                    tar -c -z -f "${package_for_host}" "${host_install_prefix/#\/}"
+                    tar -c -J -f "${package_for_host}" "${host_install_prefix/#\/}"
             else
                 with_pushd "${host_install_destdir}" \
-                    tar -c -z -f "${package_for_host}" --owner=0 --group=0 "${host_install_prefix/#\/}"
+                    tar -c -J -f "${package_for_host}" --owner=0 --group=0 "${host_install_prefix/#\/}"
             fi
         fi
         if [[ "${TEST_INSTALLABLE_PACKAGE}" ]] ; then
@@ -2803,7 +2803,7 @@ function build_and_test_installable_package() {
             call rm -rf "${PKG_TESTS_SANDBOX_PARENT}"
             call mkdir -p "${PKG_TESTS_SANDBOX}"
             with_pushd "${PKG_TESTS_SANDBOX_PARENT}" \
-                call tar xzf "${package_for_host}"
+                call tar xf "${package_for_host}"
 
             with_pushd "${PKG_TESTS_SOURCE_DIR}" \
                 call python "${LIT_EXECUTABLE_PATH}" . -sv --param package-path="${PKG_TESTS_SANDBOX}" --param filecheck="${FILECHECK_EXECUTABLE_PATH}" --param test-exec-root="${PKG_TESTS_TEMPS}"