diff --git a/Event/EventContainers/EventContainers/IdentifiableContainerMT.h b/Event/EventContainers/EventContainers/IdentifiableContainerMT.h
index 1fd416dd8eb4182729c2c562d9a09c7f51c4834c..cb1e7bb2fb375c27a159413526350881b8efa4f4 100644
--- a/Event/EventContainers/EventContainers/IdentifiableContainerMT.h
+++ b/Event/EventContainers/EventContainers/IdentifiableContainerMT.h
@@ -1,5 +1,5 @@
 /*
-  Copyright (C) 2002-2019 CERN for the benefit of the ATLAS collaboration
+  Copyright (C) 2002-2020 CERN for the benefit of the ATLAS collaboration
 */
 
 #ifndef EVENTCONTAINERS_IDENTIFIABLECONTAINERMT_H
@@ -360,8 +360,8 @@ template < class T>
 const T*
 IdentifiableContainerMT<T>::indexFindPtr( IdentifierHash hashId ) const
 {
-    if(m_mask[hashId])  return castCache()->findWait(hashId);
-    else                return nullptr;
+    if((hashId < m_mask.size()) and m_mask[hashId])  return castCache()->findWait(hashId);
+    else return nullptr;
 }
 
 // insert collection into container with id hash