diff --git a/htdocs/core/class/commondocgenerator.class.php b/htdocs/core/class/commondocgenerator.class.php
index 91da8072922a9..6ac9619024554 100644
--- a/htdocs/core/class/commondocgenerator.class.php
+++ b/htdocs/core/class/commondocgenerator.class.php
@@ -419,7 +419,7 @@ function get_substitutionarray_object($object,$outputlangs,$array_key='object')
 		}
 
 		// Fetch project information if there is a project assigned to this object
-		if ($object->element != "project" && $object->fk_project > 0)
+		if ($object->element != "project" && ! empty($object->fk_project) && $object->fk_project > 0)
 		{
 			if(!isset($object->project))
 			{