diff --git a/.travis.yml b/.travis.yml
index 4dae921..fe67a22 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -4,8 +4,7 @@ node_js:
 addons:
   apt:
     sources:
-      - ubuntu-toolchain-r-test  
-      - ppa:ubuntu-toolchain-r/test
+      - sourceline: 'ppa:ubuntu-toolchain-r/test'
     packages:
       - python
       - cmake