diff --git a/composer.json b/composer.json
index 5217f88..977fad9 100644
--- a/composer.json
+++ b/composer.json
@@ -11,13 +11,13 @@
     ],
     "require": {
         "php": "^7.1.3",
-        "guzzlehttp/guzzle": "^6.0",
+        "guzzlehttp/guzzle": "^6.0|^7.0",
         "laravel/slack-notification-channel": "^2.0"
     },
     "require-dev": {
-        "illuminate/notifications": "~5.8",
+        "illuminate/notifications": "~5.8.0|^6.0|^7.0|^8.0",
         "mockery/mockery": "^1.0",
-        "phpunit/phpunit": "^7.0"
+        "phpunit/phpunit": "^7.0|^8.0|^9.0"
     },
     "autoload": {
         "psr-4": {