diff --git a/lib/cmdlib.py b/lib/cmdlib.py
index 272f07f21a16f32fcf9242e376894a34169f51f9..6bd14b8ece06ab95c9bfd433444ab26164f975c4 100644
--- a/lib/cmdlib.py
+++ b/lib/cmdlib.py
@@ -298,7 +298,11 @@ class LogicalUnit(object):
       wanted_nodes.append(instance.primary_node)
       if not primary_only:
         wanted_nodes.extend(instance.secondary_nodes)
-    self.needed_locks[locking.LEVEL_NODE] = wanted_nodes
+
+    if self.recalculate_locks[locking.LEVEL_NODE] == constants.LOCKS_REPLACE:
+      self.needed_locks[locking.LEVEL_NODE] = wanted_nodes
+    elif self.recalculate_locks[locking.LEVEL_NODE] == constants.LOCKS_APPEND:
+      self.needed_locks[locking.LEVEL_NODE].extend(wanted_nodes)
 
     del self.recalculate_locks[locking.LEVEL_NODE]
 
diff --git a/lib/constants.py b/lib/constants.py
index c3863ea7041bfe55b8ebd28f838243327c59ec7f..ba0e1d76eed7c669b45138dc3d95b4ef6e93b0b8 100644
--- a/lib/constants.py
+++ b/lib/constants.py
@@ -190,6 +190,7 @@ REPLACE_DISK_ALL = "replace_all"
 
 # lock recalculate mode
 LOCKS_REPLACE = 'replace'
+LOCKS_APPEND = 'append'
 
 # instance creation modes
 INSTANCE_CREATE = "create"