diff --git a/.travis.yml b/.travis.yml
index 4a659c3f..bad3b2af 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -25,8 +25,14 @@ matrix:
   include:
     - php: 7.2
       env: SNIFF=1
+    - php: 5.5
+      # As the latest Debian not supporting PHP 5.5 anymore, we need to force using 'trusty'.
+      dist: trusty
+    - php: 5.4
+      # As the latest Debian not supporting PHP 5.4 anymore, we need to force using 'trusty'.
+      dist: trusty
     - php: 5.3
-      # As 'trusty' is not supporting PHP 5.2/5.3 anymore, we need to force using 'precise'.
+      # As the latest Debian not supporting PHP 5.3 anymore, we need to force using 'precise'.
       dist: precise
 
   fast_finish: true