diff --git a/src/SalesforceAuthProviderPluginBase.php b/src/SalesforceAuthProviderPluginBase.php
index 1a0e2a7327cda769e220b0bcc9e3950b1a2e4ae3..baf4ec6010d2255b4a78de1d77bf855a3be1a8c4 100644
--- a/src/SalesforceAuthProviderPluginBase.php
+++ b/src/SalesforceAuthProviderPluginBase.php
@@ -280,7 +280,7 @@ abstract class SalesforceAuthProviderPluginBase extends Salesforce implements Sa
    * {@inheritdoc}
    */
   public function getInstanceUrl() {
-    return $this->getAccessToken()->getExtraParams()['instance_url'];
+    return $this->getAccessToken()->getExtraParams()['instance_url'] ?? '';
   }
 
   /**