diff --git a/.travis.yml b/.travis.yml
index cf8b30e..d492de5 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -14,10 +14,14 @@ env:
       - PREFER_LOWEST="--prefer-lowest"
       - PREFER_LOWEST=""
     include:
-      - env: TASKWARRIOR=2.4.0
-      - env: TASKWARRIOR=2.4.1
-      - env: TASKWARRIOR=2.4.2
-      - env: TASKWARRIOR=2.4.3
+      - php: 5.6
+        env: TASKWARRIOR=2.4.0
+      - php: 5.6
+        env: TASKWARRIOR=2.4.1
+      - php: 5.6
+        env: TASKWARRIOR=2.4.2
+      - php: 5.6
+        env: TASKWARRIOR=2.4.3
 
 before_install:
   - wget http://taskwarrior.org/download/task-$TASKWARRIOR.tar.gz