diff --git a/lib/constants.py b/lib/constants.py
index ddeb6a7c15f2322c4a9672b0aa150c90f18e5d92..8dbcae5cb53177eae17db61fc51abfd72dafbd74 100644
--- a/lib/constants.py
+++ b/lib/constants.py
@@ -380,6 +380,7 @@ DTS_INT_MIRROR = compat.UniqueFrozenset([DT_DRBD8])
 
 # the set of externally-mirrored disk templates (e.g. SAN, NAS)
 DTS_EXT_MIRROR = compat.UniqueFrozenset([
+  DT_DISKLESS, # 'trivially' externally mirrored
   DT_SHARED_FILE,
   DT_BLOCK,
   DT_RBD,