diff --git a/composer.json b/composer.json
index 9977aba6..eec45094 100644
--- a/composer.json
+++ b/composer.json
@@ -38,13 +38,17 @@
 		"psr/log": "^1.1 || ^2.0 || ^3.0"
 	},
 	"require-dev": {
-		"guzzlehttp/psr7": "^2.6",
+		"chillerlan/php-dotenv": "^3.0",
+		"guzzlehttp/guzzle": "^7.8",
 		"monolog/monolog": "^3.5",
 		"phan/phan": "^5.4",
 		"phpmd/phpmd": "^2.15",
 		"phpunit/phpunit": "^10.5",
 		"squizlabs/php_codesniffer": "^3.9"
 	},
+	"suggest": {
+		"chillerlan/php-httpinterface": "^6.0 - an alternative PSR Message/Client implementation"
+	},
 	"autoload": {
 		"psr-4": {
 			"chillerlan\\OAuth\\": "src/"