diff --git a/.travis.yml b/.travis.yml
index d1779203..f7e09284 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -14,3 +14,4 @@ env:
   - PUPPET_VERSION="~> 4.2.0"
   - PUPPET_VERSION="~> 4.3.0"
   - PUPPET_VERSION="~> 4"
+  - PUPPET_VERSION="~> 4" STRICT_VARIABLES="yes"