diff --git a/libethcore/EthashSealEngine.cpp b/libethcore/EthashSealEngine.cpp
index ab1b50d06..5eacfc713 100644
--- a/libethcore/EthashSealEngine.cpp
+++ b/libethcore/EthashSealEngine.cpp
@@ -66,6 +66,8 @@ void EthashSealEngine::onSealGenerated(std::function<void(bytes const&)> const&
 //		cdebug << m_farm.work().seedHash << m_farm.work().headerHash << sol.nonce << EthashAux::eval(m_farm.work().seedHash, m_farm.work().headerHash, sol.nonce).value;
 		m_sealing.m_mixHash = sol.mixHash;
 		m_sealing.m_nonce = sol.nonce;
+		if (!m_sealing.preVerify())
+			return false;
 		RLPStream ret;
 		m_sealing.streamRLP(ret);
 		_f(ret.out());