diff --git a/modules/image/image.module b/modules/image/image.module
index a9c4d02..3e97793 100644
--- a/modules/image/image.module
+++ b/modules/image/image.module
@@ -502,7 +502,7 @@ function image_field_update_instance($instance, $prior_instance) {
   if (is_array($fid_new)) {
     $fid_new = $fid_new['fid'];
   }
-  $fid_old = $prior_instance['settings']['default_image'];
+  $fid_old = isset($prior_instance['settings']['default_image']) ? $prior_instance['settings']['default_image'] : 0;
   if (is_array($fid_old)) {
     $fid_old = $fid_old['fid'];
   }