diff --git a/alethzero/MainWin.cpp b/alethzero/MainWin.cpp
index bbe9d9f02..30bbe8243 100644
--- a/alethzero/MainWin.cpp
+++ b/alethzero/MainWin.cpp
@@ -1362,11 +1362,16 @@ void Main::on_blocks_currentItemChanged()
 			s << "&nbsp;&emsp;&nbsp;Children: <b>" << details.children.size() << "</b></h5>";
 			s << "<br/>Gas used/limit: <b>" << info.gasUsed << "</b>/<b>" << info.gasLimit << "</b>";
 			s << "<br/>Coinbase: <b>" << pretty(info.coinbaseAddress).toHtmlEscaped().toStdString() << "</b> " << info.coinbaseAddress;
+			s << "<br/>Seed hash: <b>" << info.seedHash << "</b>";
+			s << "<br/>Mix hash: <b>" << info.mixHash << "</b>";
 			s << "<br/>Nonce: <b>" << info.nonce << "</b>";
 			s << "<br/>Hash w/o nonce: <b>" << info.headerHash(WithoutNonce) << "</b>";
 			s << "<br/>Difficulty: <b>" << info.difficulty << "</b>";
 			if (info.number)
-				s << "<br/>Proof-of-Work: <b>" << ProofOfWork::eval(info) << " &lt;= " << (h256)u256((bigint(1) << 256) / info.difficulty) << "</b>";
+			{
+				auto e = ProofOfWork::eval(info);
+				s << "<br/>Proof-of-Work: <b>" << e.value << " &lt;= " << (h256)u256((bigint(1) << 256) / info.difficulty) << "</b> (mixhash: " << e.mixHash.abridged() << ")";
+			}
 			else
 				s << "<br/>Proof-of-Work: <i>Phil has nothing to prove</i>";
 			s << "<br/>Parent: <b>" << info.parentHash << "</b>";
@@ -1378,9 +1383,18 @@ void Main::on_blocks_currentItemChanged()
 			for (auto u: block[2])
 			{
 				BlockInfo uncle = BlockInfo::fromHeader(u.data());
-				s << "<br/><span style=\"margin-left: 2em\">&nbsp;</span>Hash: <b>" << uncle.hash << "</b>";
-				s << "<br/><span style=\"margin-left: 2em\">&nbsp;</span>Parent: <b>" << uncle.parentHash << "</b>";
-				s << "<br/><span style=\"margin-left: 2em\">&nbsp;</span>Number: <b>" << uncle.number << "</b>";
+				char const* line = "<br/><span style=\"margin-left: 2em\">&nbsp;</span>";
+				s << line << "Hash: <b>" << uncle.hash << "</b>";
+				s << line << "Parent: <b>" << uncle.parentHash << "</b>";
+				s << line << "Number: <b>" << uncle.number << "</b>";
+				s << line << "Coinbase: <b>" << pretty(uncle.coinbaseAddress).toHtmlEscaped().toStdString() << "</b> " << uncle.coinbaseAddress;
+				s << line << "Seed hash: <b>" << uncle.seedHash << "</b>";
+				s << line << "Mix hash: <b>" << uncle.mixHash << "</b>";
+				s << line << "Nonce: <b>" << uncle.nonce << "</b>";
+				s << line << "Hash w/o nonce: <b>" << uncle.headerHash(WithoutNonce) << "</b>";
+				s << line << "Difficulty: <b>" << uncle.difficulty << "</b>";
+				auto e = ProofOfWork::eval(uncle);
+				s << line << "Proof-of-Work: <b>" << e.value << " &lt;= " << (h256)u256((bigint(1) << 256) / uncle.difficulty) << "</b> (mixhash: " << e.mixHash.abridged() << ")";
 			}
 			if (info.parentHash)
 				s << "<br/>Pre: <b>" << BlockInfo(ethereum()->blockChain().block(info.parentHash)).stateRoot << "</b>";
diff --git a/libethcore/BlockInfo.cpp b/libethcore/BlockInfo.cpp
index 71cd0d110..c04f6fc29 100644
--- a/libethcore/BlockInfo.cpp
+++ b/libethcore/BlockInfo.cpp
@@ -57,7 +57,7 @@ void BlockInfo::setEmpty()
 	timestamp = 0;
 	extraData.clear();
 	seedHash = h256();
-	mixBytes = h256();
+	mixHash = h256();
 	nonce = Nonce();
 	hash = headerHash(WithNonce);
 }
@@ -82,7 +82,7 @@ void BlockInfo::streamRLP(RLPStream& _s, IncludeNonce _n) const
 		<< parentHash << sha3Uncles << coinbaseAddress << stateRoot << transactionsRoot << receiptsRoot << logBloom
 		<< difficulty << number << gasLimit << gasUsed << timestamp << extraData << seedHash;
 	if (_n == WithNonce)
-		_s << mixBytes << nonce;
+		_s << mixHash << nonce;
 }
 
 h256 BlockInfo::headerHash(bytesConstRef _block)
@@ -111,7 +111,7 @@ void BlockInfo::populateFromHeader(RLP const& _header, bool _checkNonce)
 		timestamp = _header[field = 11].toInt<u256>();
 		extraData = _header[field = 12].toBytes();
 		seedHash = _header[field = 13].toHash<h256>();
-		mixBytes = _header[field = 14].toHash<h256>();
+		mixHash = _header[field = 14].toHash<h256>();
 		nonce = _header[field = 15].toHash<Nonce>();
 	}
 
@@ -180,7 +180,12 @@ void BlockInfo::populateFromParent(BlockInfo const& _parent)
 	gasLimit = calculateGasLimit(_parent);
 	gasUsed = 0;
 	difficulty = calculateDifficulty(_parent);
-	seedHash = number % 30 == 0 ? sha3(_parent.seedHash.asBytes() /*+ _parent.hash.asBytes()*/) : _parent.seedHash;
+	seedHash = calculateSeedHash(_parent);
+}
+
+h256 BlockInfo::calculateSeedHash(BlockInfo const& _parent) const
+{
+	return number % 30 == 0 ? sha3(_parent.seedHash.asBytes()) : _parent.seedHash;
 }
 
 u256 BlockInfo::calculateGasLimit(BlockInfo const& _parent) const
@@ -196,7 +201,7 @@ u256 BlockInfo::calculateDifficulty(BlockInfo const& _parent) const
 	if (!parentHash)
 		return c_genesisDifficulty;
 	else
-		return max<u256>(2048, timestamp >= _parent.timestamp + (c_protocolVersion == 49 ? 5 : 8) ? _parent.difficulty - (_parent.difficulty / 2048) : (_parent.difficulty + (_parent.difficulty / 2048)));
+		return max<u256>(2048, timestamp >= _parent.timestamp + 8 ? _parent.difficulty - (_parent.difficulty / 2048) : (_parent.difficulty + (_parent.difficulty / 2048)));
 }
 
 template <class N> inline N diff(N const& _a, N const& _b) { return max(_a, _b) - min(_a, _b); }
@@ -209,6 +214,9 @@ void BlockInfo::verifyParent(BlockInfo const& _parent) const
 	if (diff(gasLimit, _parent.gasLimit) <= _parent.gasLimit / 2048)
 		BOOST_THROW_EXCEPTION(InvalidGasLimit(gasLimit, calculateGasLimit(_parent), diff(gasLimit, _parent.gasLimit), _parent.gasLimit / 2048));
 
+	if (seedHash != calculateSeedHash(_parent))
+		BOOST_THROW_EXCEPTION(InvalidSeedHash());
+
 	// Check timestamp is after previous timestamp.
 	if (parentHash)
 	{
diff --git a/libethcore/BlockInfo.h b/libethcore/BlockInfo.h
index fbc459b76..d2072046d 100644
--- a/libethcore/BlockInfo.h
+++ b/libethcore/BlockInfo.h
@@ -76,7 +76,7 @@ public:
 	u256 gasUsed;
 	u256 timestamp;
 	bytes extraData;
-	h256 mixBytes;
+	h256 mixHash;
 	h256 seedHash;
 	Nonce nonce;
 
@@ -106,7 +106,7 @@ public:
 				gasUsed == _cmp.gasUsed &&
 				timestamp == _cmp.timestamp &&
 				extraData == _cmp.extraData &&
-				mixBytes == _cmp.mixBytes &&
+				mixHash == _cmp.mixHash &&
 				seedHash == _cmp.seedHash &&
 				nonce == _cmp.nonce;
 	}
@@ -123,6 +123,7 @@ public:
 
 	u256 calculateDifficulty(BlockInfo const& _parent) const;
 	u256 calculateGasLimit(BlockInfo const& _parent) const;
+	h256 calculateSeedHash(BlockInfo const& _parent) const;
 
 	/// sha3 of the header only.
 	h256 headerHash(IncludeNonce _n) const;
@@ -133,7 +134,7 @@ inline std::ostream& operator<<(std::ostream& _out, BlockInfo const& _bi)
 {
 	_out << _bi.hash << " " << _bi.parentHash << " " << _bi.sha3Uncles << " " << _bi.coinbaseAddress << " " << _bi.stateRoot << " " << _bi.transactionsRoot << " " <<
 			_bi.receiptsRoot << " " << _bi.logBloom << " " << _bi.difficulty << " " << _bi.number << " " << _bi.gasLimit << " " <<
-			_bi.gasUsed << " " << _bi.timestamp << " " << _bi.mixBytes << " " << _bi.seedHash << " " << _bi.nonce;
+			_bi.gasUsed << " " << _bi.timestamp << " " << _bi.mixHash << " " << _bi.seedHash << " " << _bi.nonce;
 	return _out;
 }
 
diff --git a/libethcore/Exceptions.h b/libethcore/Exceptions.h
index bc9441c6b..45667f44a 100644
--- a/libethcore/Exceptions.h
+++ b/libethcore/Exceptions.h
@@ -57,6 +57,7 @@ struct InvalidGasUsed: virtual dev::Exception {};
 class InvalidTransactionsHash: virtual public dev::Exception { public: InvalidTransactionsHash(h256 _head, h256 _real); h256 head; h256 real; };
 struct InvalidTransaction: virtual dev::Exception {};
 struct InvalidDifficulty: virtual dev::Exception {};
+struct InvalidSeedHash: virtual dev::Exception {};
 class InvalidGasLimit: virtual public dev::Exception { public: InvalidGasLimit(u256 _provided = 0, u256 _valid = 0, u256 _gD = 0, u256 _mD = 0): provided(_provided), valid(_valid), givenDiff(_gD), maxDiff(_mD) {} u256 provided; u256 valid; u256 givenDiff; u256 maxDiff; virtual const char* what() const noexcept; };
 class InvalidMinGasPrice: virtual public dev::Exception { public: InvalidMinGasPrice(u256 _provided = 0, u256 _limit = 0): provided(_provided), limit(_limit) {} u256 provided; u256 limit; virtual const char* what() const noexcept; };
 struct InvalidTransactionGasUsed: virtual dev::Exception {};
diff --git a/libethcore/ProofOfWork.cpp b/libethcore/ProofOfWork.cpp
index 04e4249b6..c879df2ce 100644
--- a/libethcore/ProofOfWork.cpp
+++ b/libethcore/ProofOfWork.cpp
@@ -118,16 +118,16 @@ Ethasher* Ethasher::s_this = nullptr;
 bool Ethash::verify(BlockInfo const& _header)
 {
 	bigint boundary = (bigint(1) << 256) / _header.difficulty;
-	u256 e(eval(_header, _header.nonce));
-	return e <= boundary;
+	auto e = eval(_header, _header.nonce);
+	return (u256)e.value <= boundary && e.mixHash == _header.mixHash;
 }
 
-h256 Ethash::eval(BlockInfo const& _header, Nonce const& _nonce)
+Ethash::Result Ethash::eval(BlockInfo const& _header, Nonce const& _nonce)
 {
 	auto p = Ethasher::params(_header);
 	ethash_return_value r;
 	ethash_compute_light(&r, Ethasher::get()->cache(_header).data(), &p, _header.headerHash(WithoutNonce).data(), (uint64_t)(u64)_nonce);
-	return h256(r.result, h256::ConstructFromPointer);
+	return Result{h256(r.result, h256::ConstructFromPointer), h256(r.mix_hash, h256::ConstructFromPointer)};
 }
 
 std::pair<MineInfo, Ethash::Proof> Ethash::mine(BlockInfo const& _header, unsigned _msTimeout, bool _continue, bool _turbo)
diff --git a/libethcore/ProofOfWork.h b/libethcore/ProofOfWork.h
index 7b9787f61..fdf51f0d4 100644
--- a/libethcore/ProofOfWork.h
+++ b/libethcore/ProofOfWork.h
@@ -55,12 +55,17 @@ public:
 		Nonce nonce;
 		h256 mixHash;
 	};
+	struct Result
+	{
+		h256 value;
+		h256 mixHash;
+	};
 
-	static h256 eval(BlockInfo const& _header) { return eval(_header, _header.nonce); }
-	static h256 eval(BlockInfo const& _header, Nonce const& _nonce);
+	static Result eval(BlockInfo const& _header) { return eval(_header, _header.nonce); }
+	static Result eval(BlockInfo const& _header, Nonce const& _nonce);
 	static bool verify(BlockInfo const& _header);
 	std::pair<MineInfo, Proof> mine(BlockInfo const& _header, unsigned _msTimeout = 100, bool _continue = true, bool _turbo = false);
-	static void assignResult(Proof const& _r, BlockInfo& _header) { _header.nonce = _r.nonce; _header.mixBytes = _r.mixHash; }
+	static void assignResult(Proof const& _r, BlockInfo& _header) { _header.nonce = _r.nonce; _header.mixHash = _r.mixHash; }
 
 protected:
 	Nonce m_last;