From e7433b08e5dfec2592ef2c5207918179c596d2ab Mon Sep 17 00:00:00 2001
From: jl777 <jameslee777@yahoo.com>
Date: Wed, 27 Jun 2018 08:43:08 -1100
Subject: [PATCH] Reject height 1 reorganization

---
 src/main.cpp | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/src/main.cpp b/src/main.cpp
index 2d83ac89d..c22b93fae 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -4060,7 +4060,9 @@ bool ContextualCheckBlockHeader(const CBlockHeader& block, CValidationState& sta
         // Don't accept any forks from the main chain prior to last checkpoint
         CBlockIndex* pcheckpoint = Checkpoints::GetLastCheckpoint(chainParams.Checkpoints());
         int32_t notarized_height;
-        if ( nHeight > 1 )
+        if ( nHeight == 1 && chainActive.Tip() != 0 && chainActive.Tip()->nHeight > 1 )
+            return(false)
+        if ( nHeight != 0 )
         {
             if ( pcheckpoint != 0 && nHeight < pcheckpoint->nHeight )
                 return state.DoS(1, error("%s: forked chain older than last checkpoint (height %d) vs %d", __func__, nHeight,pcheckpoint->nHeight));