diff --git a/.travis.yml b/.travis.yml
index 39bfab8..15cf205 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -13,7 +13,7 @@ addons:
   apt:
     sources:
       - ubuntu-toolchain-r-test
-      - sourceline: 'george-edison55/cmake-3.x'
+      - sourceline: 'ppa:george-edison55/cmake-3.x'
     packages:
       - gcc-5
       - g++-5