Try testing on PHP master branch builds too (allowed failures)
diff --git a/.travis.yml b/.travis.yml
index 8f7838b..88c7742 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -9,6 +9,7 @@
   - 7.0
   - 7.1
   - 7.2
+  - master
   - hhvm
   
 env:
@@ -33,6 +34,7 @@
 matrix:
   allow_failures:
     - php: hhvm
+    - php: master
   exclude:
     - php: hhvm
       env: DB=pgsql
@@ -44,6 +46,8 @@
       env: DB=mysql
     - php: 7.2
       env: DB=mysql
+    - php: master
+      env: DB=mysql
 
 branches:
   only: