diff --git a/og_statistics.module b/og_statistics.module
--- a/og_statistics.module
+++ b/og_statistics.module
@@ -98,7 +98,7 @@
     case 'update':
       // Update statistics.
       if (og_is_group_post_type($node->type)) {
-        if (isset($node->og_groups)) {
+        if (isset($node->og_groups) && isset($node->og_initial_groups)) {
           $updated_gid = array_intersect($node->og_groups, $node->og_initial_groups);
           $added_gid = array_diff($node->og_groups, $node->og_initial_groups);
           $removed_gid = array_diff($node->og_initial_groups, $node->og_groups);