diff -u b/src/Plugin/migrate/process/EntityLookup.php b/src/Plugin/migrate/process/EntityLookup.php
--- b/src/Plugin/migrate/process/EntityLookup.php
+++ b/src/Plugin/migrate/process/EntityLookup.php
@@ -216,13 +216,15 @@
           case 'entity_reference':
             if (empty($this->lookupBundle)) {
               $handlerSettings = $fieldConfig->getSetting('handler_settings');
-              $bundles = array_filter((array) $handlerSettings['target_bundles']);
-              if (count($bundles) == 1) {
-                $this->lookupBundle = reset($bundles);
-              }
-              // This was added in 8.1.x is not supported in 8.0.x.
-              elseif (!empty($handlerSettings['auto_create']) && !empty($handlerSettings['auto_create_bundle'])) {
-                $this->lookupBundle = reset($handlerSettings['auto_create_bundle']);
+              if (count($handlerSettings) > 0) {
+                $bundles = array_filter((array) $handlerSettings['target_bundles']);
+                if (count($bundles) == 1) {
+                  $this->lookupBundle = reset($bundles);
+                }
+                // This was added in 8.1.x is not supported in 8.0.x.
+                elseif (!empty($handlerSettings['auto_create']) && !empty($handlerSettings['auto_create_bundle'])) {
+                  $this->lookupBundle = reset($handlerSettings['auto_create_bundle']);
+                }
               }
             }