diff --git a/.travis.yml b/.travis.yml
index 77eed441..b22f6a26 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -5,6 +5,7 @@ php:
   - 7.2
   - 7.3
   - 7.4
+  - nightly
 
 cache:
   directories:
diff --git a/composer.json b/composer.json
index 00b6fe9e..5e966ed9 100644
--- a/composer.json
+++ b/composer.json
@@ -66,7 +66,7 @@
         "jpgraph/jpgraph": "^4.0",
         "mpdf/mpdf": "^8.0",
         "phpcompatibility/php-compatibility": "^9.3",
-        "phpunit/phpunit": "^8.5",
+        "phpunit/phpunit": "^8.5|^9.3",
         "squizlabs/php_codesniffer": "^3.5",
         "tecnickcom/tcpdf": "^6.3"
     },