diff --git a/libethcore/BlockInfo.cpp b/libethcore/BlockInfo.cpp
index fec010c2d..ce158c3cc 100644
--- a/libethcore/BlockInfo.cpp
+++ b/libethcore/BlockInfo.cpp
@@ -134,7 +134,7 @@ void BlockInfo::populate(bytesConstRef _block, bool _checkNonce)
 	RLP header = root[0];
 
 	if (!header.isList())
-		BOOST_THROW_EXCEPTION(InvalidBlockFormat(0,header.data()) << errinfo_comment("block header needs to be a list"));
+		BOOST_THROW_EXCEPTION(InvalidBlockFormat(0, header.data()) << errinfo_comment("block header needs to be a list"));
 	populateFromHeader(header, _checkNonce);
 
 	if (!root[1].isList())
diff --git a/libethereum/BlockChain.cpp b/libethereum/BlockChain.cpp
index 29095076f..293a9d757 100644
--- a/libethereum/BlockChain.cpp
+++ b/libethereum/BlockChain.cpp
@@ -209,6 +209,11 @@ h256s BlockChain::import(bytes const& _block, OverlayDB const& _db)
 	try
 #endif
 	{
+		RLP blockRLP(_block);
+
+		if (!blockRLP.isList())
+			BOOST_THROW_EXCEPTION(InvalidBlockFormat(0,blockRLP.data()) << errinfo_comment("block header needs to be a list"));
+
 		bi.populate(&_block);
 		bi.verifyInternals(&_block);
 	}
diff --git a/libethereum/Transaction.cpp b/libethereum/Transaction.cpp
index 96689326d..a89083648 100644
--- a/libethereum/Transaction.cpp
+++ b/libethereum/Transaction.cpp
@@ -36,6 +36,9 @@ Transaction::Transaction(bytesConstRef _rlpData, CheckSignature _checkSig)
 	RLP rlp(_rlpData);
 	try
 	{
+		if (!rlp.isList())
+			BOOST_THROW_EXCEPTION(BadRLP() << errinfo_comment("transaction RLP must be a list"));
+
 		m_nonce = rlp[field = 0].toInt<u256>();
 		m_gasPrice = rlp[field = 1].toInt<u256>();
 		m_gas = rlp[field = 2].toInt<u256>();