Do not use ninja on OSX
diff --git a/.travis.yml b/.travis.yml
index 4334a9e..6f6e725 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -30,10 +30,12 @@
     compiler: gcc
     env:
       TARGET=x86_64-osx
+      CMAKE_GENERATOR="Unix Makefiles"
   - os: osx
     compiler: clang
     env:
       TARGET=x86_64-osx
+      CMAKE_GENERATOR="Unix Makefiles"
   - os: windows
     env:
       TARGET=x86_64-windows