diff --git a/src/ripple/app/main/Application.cpp b/src/ripple/app/main/Application.cpp
index 7d59daac27..98417e6cec 100644
--- a/src/ripple/app/main/Application.cpp
+++ b/src/ripple/app/main/Application.cpp
@@ -1078,6 +1078,7 @@ ApplicationImp::getLastFullLedger()
             return ledger;
 
         ledger->setClosed ();
+        ledger->setImmutable();
 
         if (getApp().getLedgerMaster ().haveLedger (ledgerSeq))
         {