diff --git a/composer.json b/composer.json
index 2aba1865..be1bbf7b 100644
--- a/composer.json
+++ b/composer.json
@@ -11,7 +11,7 @@
 		"phpcompatibility/phpcompatibility-wp": "*",
 		"squizlabs/php_codesniffer": "*",
 		"wp-coding-standards/wpcs": "*",
-		"wp-phpunit/wp-phpunit": "5.7.2",
+		"wp-phpunit/wp-phpunit": "6.6.1",
 		"phpunit/phpunit": "7.5.20",
 		"yoast/phpunit-polyfills": "^1.0"
 	  },