diff --git a/.travis.yml b/.travis.yml
index 269e4d4..a7b7761 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -37,10 +37,13 @@ matrix:
             - llvm-toolchain-trusty-5.0
           packages:
             - clang-5.0
+    - os: osx
+      osx_image: xcode9
 
 # prevent Travis from overwriting our CXX variables
 before_install:
     - eval "${MATRIX_EVAL}"
+    - echo $CXX
 
 script:
     - mkdir build