diff --git a/.travis.yml b/.travis.yml
index 881c6e2..91077bc 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -5,8 +5,16 @@ php:
   - 7.3
   - 7.4
 
+jobs:
+  fast_finish: true
+
+env:
+  matrix:
+    - COMPOSER_FLAGS="--prefer-lowest"
+    - COMPOSER_FLAGS=""
+
 before_script:
   - travis_retry composer self-update
-  - travis_retry composer install --prefer-source --no-interaction --dev
+  - travis_retry composer update ${COMPOSER_FLAGS} --no-interaction --prefer-source
 
 script: phpunit
diff --git a/composer.json b/composer.json
index eb15f70..6a6cb82 100644
--- a/composer.json
+++ b/composer.json
@@ -25,7 +25,7 @@
   },
   "require-dev": {
     "orchestra/testbench": "^5.3",
-    "phpunit/phpunit": "^7.2|^7.5|^9.2"
+    "phpunit/phpunit": "^8.5"
   },
   "autoload": {
     "psr-4": {