diff --git a/.travis.yml b/.travis.yml
index 46c68aa..1e8fbc2 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -15,6 +15,8 @@ env:
   jobs:
     - IMAGE=alpine IMAGE_TAG=latest
     - IMAGE=archlinux IMAGE_TAG=latest
+    # 18.04 (Bionic) is the oldest one we want to attempt builds with.
+    - IMAGE=ubuntu IMAGE_TAG=bionic
     - IMAGE=ubuntu IMAGE_TAG=latest
     - IMAGE=ubuntu IMAGE_TAG=rolling
     - IMAGE=ubuntu IMAGE_TAG=devel