diff --git a/.travis.yml b/.travis.yml
index cecd996..33c7e7d 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -20,8 +20,23 @@ matrix:
       dist: precise
     - php: hhvm
       install: composer require phpunit/phpunit:^5 --dev --no-interaction
+    - name: "Mac OS X"
+      os: osx
+      language: generic # no built-in php support
+      before_install:
+      - brew install php || brew install php # retry if it doesn't work on first try
+      - brew install composer
+    - name: "Windows"
+      os: windows
+      language: shell # no built-in php support
+      before_install:
+        - choco install php
+        - choco install composer
+        - export PATH="$(powershell -Command '("Process", "Machine" | % { [Environment]::GetEnvironmentVariable("PATH", $_) -Split ";" -Replace "\\$", "" } | Select -Unique | % { cygpath $_ }) -Join ":"')"
   allow_failures:
     - php: hhvm
+    - os: osx
+    - os: windows
 
 sudo: false