diff --git a/.travis.yml b/.travis.yml
index d3db55772..9db52849a 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -14,7 +14,7 @@ matrix:
             - llvm-toolchain-precise-3.8
             - ubuntu-toolchain-r-test
     - os: linux
-      env: COMPILER_NAME=clang CXX=clang++-3.8 CC=clang-3.8 EXTRA_FLAGS="-stdlib=libc++"
+      env: COMPILER_NAME=clang CXX=clang++-3.8 CC=clang-3.8 CXXFLAGS="-stdlib=libc++"
       addons:
         apt:
           packages: