diff --git a/Sources/Plugins/AttachmentManager/AttachmentManager.swift b/Sources/Plugins/AttachmentManager/AttachmentManager.swift
index 826e122a..a0ce919d 100755
--- a/Sources/Plugins/AttachmentManager/AttachmentManager.swift
+++ b/Sources/Plugins/AttachmentManager/AttachmentManager.swift
@@ -202,14 +202,21 @@ extension AttachmentManager: UICollectionViewDataSource, UICollectionViewDelegat
     
     final public func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize {
         
-        if let customSize = self.dataSource?.attachmentManager(self, sizeFor: self.attachments[indexPath.row], at: indexPath.row){
-            return customSize
-        }
-        
         var height = attachmentView.intrinsicContentHeight
         if let layout = collectionView.collectionViewLayout as? UICollectionViewFlowLayout {
             height -= (layout.sectionInset.bottom + layout.sectionInset.top + collectionView.contentInset.top + collectionView.contentInset.bottom)
         }
+        
+        // Prevent out of range error when the AttachmentCell has not been added the attachment array
+        if indexPath.row == attachments.count && showAddAttachmentCell {
+            return CGSize(width: height, height: height)
+        }
+        
+        let attachment = self.attachments[indexPath.row]
+        if let customSize = self.dataSource?.attachmentManager(self, sizeFor: attachment, at: indexPath.row){
+            return customSize
+        }
+        
         return CGSize(width: height, height: height)
     }