diff --git a/src/BaseClient.php b/src/BaseClient.php
index d232858..9da0bc1 100644
--- a/src/BaseClient.php
+++ b/src/BaseClient.php
@@ -274,7 +274,7 @@ protected function requestToken(string $clientId, string $clientSecret, TokenReq
                 'Accept' => 'application/json',
                 'Authorization' => sprintf('Basic %s', $credentials)
             ],
-            'query' => $token->toArray()
+            'body' => $token->toArray()
         ]);
 
         $responseTypes = [
diff --git a/tests/BaseClientTest.php b/tests/BaseClientTest.php
index d97327c..cfdcf60 100644
--- a/tests/BaseClientTest.php
+++ b/tests/BaseClientTest.php
@@ -234,7 +234,7 @@ protected function authenticateByClientCredentials(?ResponseInterface $response
                 'Accept' => 'application/json',
                 'Authorization' => 'Basic ' . $credentials
             ],
-            'query' => [
+            'body' => [
                 'grant_type' => 'client_credentials'
             ]
         ])->willReturn($response);
@@ -375,7 +375,7 @@ protected function authenticateByAuthorizationCode(?ResponseInterface $response
                 'Accept' => 'application/json',
                 'Authorization' => 'Basic ' . $credentials
             ],
-            'query' => [
+            'body' => [
                 'grant_type' => 'authorization_code',
                 'code' => '123456',
                 'redirect_uri' => 'http://someserver.xxx/redirect',
@@ -430,7 +430,7 @@ protected function authenticateByRefreshToken(?ResponseInterface $response = nul
                 'Accept' => 'application/json',
                 'Authorization' => 'Basic ' . $credentials
             ],
-            'query' => [
+            'body' => [
                 'grant_type' => 'refresh_token',
                 'refresh_token' => $this->validRefreshToken->getToken()
             ]
diff --git a/tests/ClientTest.php b/tests/ClientTest.php
index 96a73b2..bf839ab 100644
--- a/tests/ClientTest.php
+++ b/tests/ClientTest.php
@@ -43,7 +43,7 @@ protected function authenticateByClientCredentials()
                 'Accept' => 'application/json',
                 'Authorization' => 'Basic ' . $credentials
             ],
-            'query' => [
+            'body' => [
                 'grant_type' => 'client_credentials'
             ]
         ])->willReturn($response);