From e4dba36892477f3ef614dd4e4f1234ae4a4e26d0 Mon Sep 17 00:00:00 2001
From: obscuren <geffobscura@gmail.com>
Date: Thu, 30 Apr 2015 14:55:21 +0200
Subject: [PATCH] core: check for parent in calc TD. TD = (N != 0 == parent.TD)
 || (== D)

---
 core/chain_manager.go | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/core/chain_manager.go b/core/chain_manager.go
index e97ed307ce..9f62d3b47d 100644
--- a/core/chain_manager.go
+++ b/core/chain_manager.go
@@ -49,6 +49,10 @@ func CalcDifficulty(block, parent *types.Header) *big.Int {
 }
 
 func CalculateTD(block, parent *types.Block) *big.Int {
+	if parent == nil {
+		return block.Difficulty()
+	}
+
 	td := new(big.Int).Add(parent.Td, block.Header().Difficulty)
 
 	return td