diff --git a/app/controllers/course/lti.php b/app/controllers/course/lti.php
index ab71e46a792c8c0252bef6e6ce2e4dddf1a6efa0..01c57ded24cf7dca2f34908f0ecad267ddaae4de 100644
--- a/app/controllers/course/lti.php
+++ b/app/controllers/course/lti.php
@@ -242,7 +242,7 @@ class Course_LtiController extends StudipController
         ]);
 
         foreach ($custom_parameters as $param) {
-            list($key, $value) = explode('=', $param);
+            list($key, $value) = explode('=', $param, 2);
             if (isset($value)) {
                 $lti_link->addCustomParameter(trim($key), trim($value));
             }
@@ -351,7 +351,7 @@ class Course_LtiController extends StudipController
         ]);
 
         foreach ($custom_parameters as $param) {
-            list($key, $value) = explode('=', $param);
+            list($key, $value) = explode('=', $param, 2);
             if (isset($value)) {
                 $lti_link->addCustomParameter(trim($key), trim($value));
             }
diff --git a/lib/classes/LtiLink.php b/lib/classes/LtiLink.php
index d62c01c914268c715afebbb73fb655dc4e8e44bd..546a5339d3965c0fcb8bd988199cc91781c8e90a 100644
--- a/lib/classes/LtiLink.php
+++ b/lib/classes/LtiLink.php
@@ -51,6 +51,7 @@ class LtiLink
             'lti_version' => 'LTI-1p0',
             'lti_message_type' => 'basic-lti-launch-request',
             'oauth_consumer_key' => $this->consumer_key,
+            'oauth_callback' => 'about:blank',
             'oauth_version' => '1.0',
             'oauth_nonce' => uniqid('lti', true),
             'oauth_timestamp' => time(),