diff --git a/core/model/SiteTree.php b/core/model/SiteTree.php
index f66c60873..06f127763 100644
--- a/core/model/SiteTree.php
+++ b/core/model/SiteTree.php
@@ -1,4 +1,5 @@
 <?php
+
 /**
  * @package sapphire
  * @subpackage core
@@ -490,6 +491,12 @@ class SiteTree extends DataObject {
 			}
 		}
 
+
+		// If priority is empty or invalid, set it to the default value
+		if(!is_numeric($this->Priority) ||
+			 (($this->Priority < 0) || ($this->Priority > 1)))
+			$this->Priority = self::$defaults['Priority'];
+
 		parent::onBeforeWrite();
 	}