diff --git a/.travis.yml b/.travis.yml
index fd24e1caa..6ab494aa3 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -9,7 +9,7 @@ install:
   - sudo apt-get install libcairo2-dev # for utils
   - sudo apt-get install libicu-dev # for extra unicode functions
   - sudo apt-get install libgraphite2-dev # for extra shapers
-script: ./autogen.sh && make && make check
+script: ./autogen.sh && make CPPFLAGS=-Werror && make check CPPFLAGS=-Werror
 notifications:
   irc: "irc.freenode.org#harfbuzz"
   email: harfbuzz@lists.freedesktop.org