diff --git a/composer.json b/composer.json
index 6f4ed92a5db219fbabb902e545b48e7dc204ffda..739593dc0daf4045d3610e303626c631ab5c2591 100644
--- a/composer.json
+++ b/composer.json
@@ -11,7 +11,7 @@
     },
     "require-dev": {
         "php": ">=5.5",
-        "phpunit/phpunit": "^8 | ^9",
+        "phpunit/phpunit": "^8",
         "mockery/mockery": "*",
         "10up/wp_mock": "*",
         "wimg/php-compatibility": "^8",