diff --git a/tbl_zoom_select.php b/tbl_zoom_select.php
index c28474b3cb..e0a69728d1 100644
--- a/tbl_zoom_select.php
+++ b/tbl_zoom_select.php
@@ -217,6 +217,7 @@ if (isset($zoom_submit)
 
         $data[] = $tmpData;
     }
+    unset($tmpData);
     /*
      * Form for displaying point data and also the scatter plot
      */