diff --git a/src/LatLongField.php b/src/LatLongField.php
index 49ef55b..9b7a7e0 100644
--- a/src/LatLongField.php
+++ b/src/LatLongField.php
@@ -105,7 +105,7 @@ public function getAddressInputFields()
             // String
             if(is_string($field)) $ret[] = ArrayData::create(array('value' => $field));
             // pointer to FormField (use getName())
-            if(is_object($field) && $field->is_a(FormField::class)){
+            if(is_object($field) && is_a($field, FormField::class)){
                 $ret[] = ArrayData::create(array('value' => $field->getName()));
             }
         }