diff --git a/resources/inc/class.resources_bo.inc.php b/resources/inc/class.resources_bo.inc.php
index 6f873c0733..3fdbaea1f6 100755
--- a/resources/inc/class.resources_bo.inc.php
+++ b/resources/inc/class.resources_bo.inc.php
@@ -750,7 +750,7 @@ class resources_bo
 					$end = $start->format('ts') + 86399;
 				} else {
 					$start = $start->format('ts');
-					$end = $start + ($cal_info['duration']);
+					$end = $start + (int)$cal_info['duration'];
 				}
 
 				// search events matching our timestamps