diff --git a/.travis.yml b/.travis.yml
index b4850b7..10bc8d0 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -3,6 +3,8 @@ language: cpp
 
 addons:
   apt:
+    sources:
+    - ubuntu-toolchain-r-test
     packages:
     - gcc-4.9
     - g++-4.9