diff --git a/.travis.yml b/.travis.yml
index e63ce75e..547b8f87 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -14,7 +14,10 @@ env:
 
 addons:
   apt:
+    sources:
+      - llvm-toolchain-trusty-4.0
     packages:
+      - clang-4.0
       - docbook2x
       - dos2unix