diff --git a/.travis.yml b/.travis.yml
index 607524e8..3fc5c0d6 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -11,6 +11,7 @@ matrix:
       apt:
         sources:
         - llvm-toolchain-precise-3.5
+        - ubuntu-toolchain-r-test
         packages:
         - clang-3.5
   - compiler: gcc