diff --git a/.travis.yml b/.travis.yml
index bac3823e..2500770b 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -29,6 +29,9 @@ branches:
 
 matrix:
     fast_finish: true
+    include:
+        - php: 5.6
+          env: COMPOSER_FLAGS="--prefer-stable --prefer-lowest" COVERAGE=true
 
 before_install:
     - if [[ $COVERAGE != true ]]; then phpenv config-rm xdebug.ini || true; fi