diff --git a/configuration.sh b/configuration.sh
index db42a7a..79119dd 100644
--- a/configuration.sh
+++ b/configuration.sh
@@ -160,6 +160,9 @@ DRUPAL_TESTING_INSTALLATION_FORM_VALUES=${DRUPAL_TESTING_INSTALLATION_FORM_VALUE
 # versions of dependencies are installed.
 DRUPAL_TESTING_MIN_BUILD=${DRUPAL_TESTING_MIN_BUILD:-false}
 
+# Use the lenient drupal packagist endpoint.
+DRUPAL_TESTING_USE_LENIENT_ENDPOINT=${DRUPAL_TESTING_USE_LENIENT_ENDPOINT:-false}
+
 # The symfony environment variable to ignore deprecations, for possible values see symfony documentation.
 # The default value is "week" to ignore any deprecation notices.
 export SYMFONY_DEPRECATIONS_HELPER=${SYMFONY_DEPRECATIONS_HELPER-weak}
diff --git a/lib/stages/prepare_build.sh b/lib/stages/prepare_build.sh
index 964171e..33f1dc4 100644
--- a/lib/stages/prepare_build.sh
+++ b/lib/stages/prepare_build.sh
@@ -55,6 +55,9 @@ _stage_prepare_build() {
     jq '.repositories[0].options.symlink = false' "${DRUPAL_TESTING_DRUPAL_INSTALLATION_DIRECTORY}""/composer.json" | awk 'BEGIN{RS="";getline<"-";print>ARGV[1]}' "${DRUPAL_TESTING_DRUPAL_INSTALLATION_DIRECTORY}""/composer.json"
 
     composer config repositories.1 composer https://asset-packagist.org --working-dir="${DRUPAL_TESTING_DRUPAL_INSTALLATION_DIRECTORY}"
+    if [ "${DRUPAL_TESTING_USE_LENIENT_ENDPOINT}" = true ]; then
+      composer config repositories.lenient composer https://packages.drupal.org/lenient --working-dir="${DRUPAL_TESTING_DRUPAL_INSTALLATION_DIRECTORY}"
+    fi
     composer config repositories.2 composer https://packages.drupal.org/8 --working-dir="${DRUPAL_TESTING_DRUPAL_INSTALLATION_DIRECTORY}"
 
     # Enable patching