diff --git a/src/Form/SharethisConfigurationForm.php b/src/Form/SharethisConfigurationForm.php
index fc99425..3876b27 100644
--- a/src/Form/SharethisConfigurationForm.php
+++ b/src/Form/SharethisConfigurationForm.php
@@ -237,7 +237,7 @@ public function buildForm(array $form, FormStateInterface $form_state) {
         '#description' => t('Select which view modes the ShareThis widget should appear on for %label nodes.', array('%label' => $bundle_info['label'])),
         '#type' => 'checkboxes',
         '#options' => $modes,
-        '#default_value' => $config->get('sharethisnodes.' . $bundle),
+        '#default_value' => $config->get('sharethisnodes.' . $bundle) ?: [],
       );
     }
     // Allow the user to choose which content types will have ShareThis added