diff --git a/.travis.yml b/.travis.yml
index 1d8f631..6f7574f 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -25,12 +25,14 @@ env:
     - RACKET_VERSION=7.0
     - RACKET_VERSION=7.1
     - RACKET_VERSION=HEAD
+    - RACKET_VERSION=HEADCS
 
 # You may want to test against certain versions of Racket, without
 # having them count against the overall success/failure.
 matrix:
   allow_failures:
     # - env: RACKET_VERSION=HEAD
+    - RACKET_VERSION=HEADCS
   # Fast finish: Overall build result is determined as soon as any of
   # its rows have failed, or, all of its rows that aren't allowed to
   # fail have succeeded.