diff --git a/.travis.yml b/.travis.yml
index e93f3556..fab5b6c2 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -13,11 +13,11 @@ install:
   - tar -xzf elasticsearch-${ES_VERSION}.tar.gz
   - ./elasticsearch-${ES_VERSION}/bin/elasticsearch -d
 before_script:
-  - composer config -g github-oauth.github.com $GITHUB_COMPOSER_AUTH
+  - if [ "$GITHUB_COMPOSER_AUTH" ]; then composer config -g github-oauth.github.com $GITHUB_COMPOSER_AUTH; fi
   - composer install --no-interaction --prefer-dist
 script:
   - wget -q --waitretry=1 --retry-connrefused -T 10 -O - http://127.0.0.1:9200
   - vendor/bin/phpunit --coverage-clover=coverage.clover
   - vendor/bin/phpcs -p --standard=PSR2 --ignore=vendor/ ./
 after_script:
-  - travis_retry php vendor/bin/coveralls
\ No newline at end of file
+  - travis_retry php vendor/bin/coveralls
diff --git a/composer.json b/composer.json
index 62b062c1..78e05f25 100644
--- a/composer.json
+++ b/composer.json
@@ -12,7 +12,7 @@
     ],
     "require": {
         "php": ">=5.6",
-        "symfony/serializer": "~2.7|~3.0|~4.0",
+        "symfony/serializer": "~2.7|~3.0|~4.0|~5.0",
         "paragonie/random_compat": "*",
         "elasticsearch/elasticsearch": "~5.0"
     },