diff --git a/src/CrowdinApiClient/Api/GraphqlApi.php b/src/CrowdinApiClient/Api/GraphqlApi.php
index 2d155a8b..eb6ed0b4 100644
--- a/src/CrowdinApiClient/Api/GraphqlApi.php
+++ b/src/CrowdinApiClient/Api/GraphqlApi.php
@@ -33,7 +33,8 @@ public function query(string $query, ?string $operationName = null, ?array $vari
         ];
 
         $response = $this->client->getClient()->request('post', $this->getFullUrl(), $options);
-        $response = json_decode($response, true);
+        // GuzzleHttpClient returns a stream, not a string
+        $response = json_decode((string)$response, true);
 
         $this->client->getResponseErrorHandler()->check($response);
 
diff --git a/tests/CrowdinApiClient/Api/GraphqlApiTest.php b/tests/CrowdinApiClient/Api/GraphqlApiTest.php
index 1b30ac30..dd2044e0 100644
--- a/tests/CrowdinApiClient/Api/GraphqlApiTest.php
+++ b/tests/CrowdinApiClient/Api/GraphqlApiTest.php
@@ -2,8 +2,24 @@
 
 namespace CrowdinApiClient\Tests\Api;
 
+use CrowdinApiClient\Http\Client\GuzzleHttpClient;
+use GuzzleHttp\Client;
+use GuzzleHttp\Handler\MockHandler;
+use GuzzleHttp\Psr7\Response;
+
 class GraphqlApiTest extends AbstractTestApi
 {
+    public function testQueryWithGuzzleClient(): void
+    {
+        $responseBody = json_encode(['data' => ['viewer' => ['id' => 1]]]);
+        $handler = new MockHandler([new Response(200, [], $responseBody)]);
+        $this->crowdin->setClient(new GuzzleHttpClient(new Client(['handler' => $handler])));
+
+        $response = $this->crowdin->graphql->query('query { viewer { id } }');
+
+        $this->assertSame(['viewer' => ['id' => 1]], $response);
+    }
+
     public function testQuery(): void
     {
         $query = 'query Test($limit: Int) {