diff --git a/.travis.yml b/.travis.yml
index ecb6f5c..e6a02fd 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -2,6 +2,8 @@ language: php
 
 addons:
   apt:
+    sources:
+    - ubuntu-toolchain-r-test
     packages:
     - gcc-4.8
     - g++-4.8