diff --git a/.travis.yml b/.travis.yml
index 21deaa0..8c3fc57 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -4,6 +4,11 @@ php:
   - 7.1
   - 7.2
 
+env:
+  matrix:
+    - COMPOSER_FLAGS="--prefer-lowest"
+    - COMPOSER_FLAGS=""
+
 before_script:
   - composer install --dev --prefer-source --no-interaction