diff --git a/.travis.yml b/.travis.yml
index 238174a4e4..fa50e30ef7 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -1,4 +1,6 @@
 language: csharp
 sudo: false
+mono:
+  - 4.0.5
 script:
   - ./build.sh --quiet verify