diff --git a/htest/Test/Ganeti/OpCodes.hs b/htest/Test/Ganeti/OpCodes.hs
index a1631e58d0fdeba64c945e61596669402ca47249..b9398ecc1ebaf5cdcfd8baaebc44d8c572e7d624 100644
--- a/htest/Test/Ganeti/OpCodes.hs
+++ b/htest/Test/Ganeti/OpCodes.hs
@@ -219,7 +219,8 @@ instance Arbitrary OpCodes.OpCode where
           genMaybe genNodeNameNE <*> genMaybe genNameNE <*>
           arbitrary <*> arbitrary <*> (genTags >>= mapM mkNonEmpty)
       "OP_INSTANCE_MULTI_ALLOC" ->
-        OpCodes.OpInstanceMultiAlloc <$> genMaybe genNameNE <*> pure []
+        OpCodes.OpInstanceMultiAlloc <$> genMaybe genNameNE <*> pure [] <*>
+          arbitrary
       "OP_INSTANCE_REINSTALL" ->
         OpCodes.OpInstanceReinstall <$> genFQDN <*> arbitrary <*>
           genMaybe genNameNE <*> genMaybe (pure emptyJSObject)
diff --git a/htools/Ganeti/OpCodes.hs b/htools/Ganeti/OpCodes.hs
index 03b606997ba48b9ebbdcfa4ee25e0920a7b3f2fe..1e8f561263fcb519fe55aba4258636b4d2cc6cd3 100644
--- a/htools/Ganeti/OpCodes.hs
+++ b/htools/Ganeti/OpCodes.hs
@@ -300,6 +300,7 @@ $(genOpCode "OpCode"
   , ("OpInstanceMultiAlloc",
      [ pIallocator
      , pMultiAllocInstances
+     , pOpportunisticLocking
      ])
   , ("OpInstanceReinstall",
      [ pInstanceName