diff --git a/.travis.yml b/.travis.yml
index b92cc4a..27cea52 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -14,6 +14,8 @@ addons:
 matrix:
   include:
     - env: COMPILER=g++-5
+      os: linux
+      language: cpp
       addons:
         apt:
           sources:
@@ -22,6 +24,8 @@ matrix:
             - *default_packages
             - g++-5
     - env: COMPILER=g++-6
+      os: linux
+      language: cpp
       addons:
         apt:
           sources: