Update .travis.yml
diff --git a/.travis.yml b/.travis.yml
index 46715f9..9e2b885 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -70,6 +70,11 @@
 stages:
   - format_analyzer_tests
 
+os:
+  - linux
+  - osx
+  - windows
+  
 # Only building master means that we don't run two builds for each pull request.
 branches:
   only: