diff --git a/lib/cmdlib.py b/lib/cmdlib.py
index 5b065e813f81fc65451d0bac71bdd334738154f1..5eae4a85e2d2395ab916a9d65de1c86ac769941f 100644
--- a/lib/cmdlib.py
+++ b/lib/cmdlib.py
@@ -13589,7 +13589,7 @@ class LUGroupAdd(LogicalUnit):
                               constants.DISK_DT_TYPES)
       self.new_diskparams = self.op.diskparams
     else:
-      self.new_diskparams = None
+      self.new_diskparams = {}
 
     if self.op.ipolicy:
       cluster = self.cfg.GetClusterInfo()
diff --git a/lib/objects.py b/lib/objects.py
index 8cc31e79424205404df91dc20d9d6d12c9e69122..9b086ded93651acf43966da172ea9af60a8f7261 100644
--- a/lib/objects.py
+++ b/lib/objects.py
@@ -1496,7 +1496,8 @@ class NodeGroup(TaggableObject):
     if self.mtime is None:
       self.mtime = time.time()
 
-    self.diskparams = UpgradeDiskParams(self.diskparams)
+    if self.diskparams is None:
+      self.diskparams = {}
     if self.ipolicy is None:
       self.ipolicy = MakeEmptyIPolicy()