diff --git a/laff-pack.php b/laff-pack.php
index 17dba0b..df4824a 100644
--- a/laff-pack.php
+++ b/laff-pack.php
@@ -63,6 +63,7 @@ function __construct($boxes = null, $container = null)
 					$this->container_dimensions['width'] = $container['width'];
 					
 					// Note: do NOT set height, it will be calculated on-the-go
+					$this->container_dimensions['height'] = 0;
 				}
 			}
 		}
@@ -97,6 +98,7 @@ function pack($boxes = null, $container = null) {
 				$this->container_dimensions['width'] = $container['width'];
 				
 				// Note: do NOT set height, it will be calculated on-the-go
+				$this->container_dimensions['height'] = 0;
 			}
 		}