diff --git a/bootstrapvz/common/fs/virtualdiskimage.py b/bootstrapvz/common/fs/virtualdiskimage.py
index b36c8fc..62b3f09 100644
--- a/bootstrapvz/common/fs/virtualdiskimage.py
+++ b/bootstrapvz/common/fs/virtualdiskimage.py
@@ -5,6 +5,7 @@ class VirtualDiskImage(QEMUVolume):
 
 	extension = 'vdi'
 	qemu_format = 'vdi'
+	# VDI format does not have an URI (check here: https://forums.virtualbox.org/viewtopic.php?p=275185#p275185)
 	ovf_uri = None
 
 	def get_uuid(self):