diff --git a/libqethereum/QEthereum.cpp b/libqethereum/QEthereum.cpp
index a71aca2b4..e77c9d632 100644
--- a/libqethereum/QEthereum.cpp
+++ b/libqethereum/QEthereum.cpp
@@ -595,7 +595,7 @@ static shh::Envelope toSealed(QString _json, shh::Message const& _m, Secret _fro
 			for (auto i: f["topic"].toArray())
 				bt.shift(asBytes(padded(i.toString(), 32)));
 	}
-	return _m.seal(_from, bt, workToProve, ttl);
+	return _m.seal(_from, bt, ttl, workToProve);
 }
 
 void QWhisper::doPost(QString _json)
diff --git a/libwhisper/WhisperHost.cpp b/libwhisper/WhisperHost.cpp
index 25c1a06bf..26ca3d93b 100644
--- a/libwhisper/WhisperHost.cpp
+++ b/libwhisper/WhisperHost.cpp
@@ -53,6 +53,9 @@ void WhisperHost::streamMessage(h256 _m, RLPStream& _s) const
 
 void WhisperHost::inject(Envelope const& _m, WhisperPeer* _p)
 {
+	if (_m.expiry() <= time(0))
+		return;
+
 	auto h = _m.sha3();
 	{
 		UpgradableGuard l(x_messages);
@@ -60,6 +63,7 @@ void WhisperHost::inject(Envelope const& _m, WhisperPeer* _p)
 			return;
 		UpgradeGuard ll(l);
 		m_messages[h] = _m;
+		m_expiryQueue[_m.expiry()] = h;
 	}
 
 //	if (_p)
@@ -109,6 +113,7 @@ unsigned WhisperHost::installWatch(shh::TopicFilter const& _f)
 
 h256s WhisperHost::watchMessages(unsigned _watchId)
 {
+	cleanup();
 	h256s ret;
 	auto wit = m_watches.find(_watchId);
 	if (wit == m_watches.end())
@@ -145,3 +150,13 @@ void WhisperHost::uninstallWatch(unsigned _i)
 		if (!--fit->second.refCount)
 			m_filters.erase(fit);
 }
+
+void WhisperHost::cleanup()
+{
+	// remove old messages.
+	// should be called every now and again.
+	auto now = time(0);
+	WriteGuard l(x_messages);
+	for (auto it = m_expiryQueue.begin(); it != m_expiryQueue.end() && it->first <= now; it = m_expiryQueue.erase(it))
+		m_messages.erase(it->second);
+}
diff --git a/libwhisper/WhisperHost.h b/libwhisper/WhisperHost.h
index 9ad859967..2eb4856ee 100644
--- a/libwhisper/WhisperHost.h
+++ b/libwhisper/WhisperHost.h
@@ -55,11 +55,13 @@ public:
 	virtual unsigned installWatchOnId(h256 _filterId) override;
 	virtual void uninstallWatch(unsigned _watchId) override;
 	virtual h256s peekWatch(unsigned _watchId) const override { dev::Guard l(m_filterLock); try { return m_watches.at(_watchId).changes; } catch (...) { return h256s(); } }
-	virtual h256s checkWatch(unsigned _watchId) override { dev::Guard l(m_filterLock); h256s ret; try { ret = m_watches.at(_watchId).changes; m_watches.at(_watchId).changes.clear(); } catch (...) {} return ret; }
+	virtual h256s checkWatch(unsigned _watchId) override { cleanup(); dev::Guard l(m_filterLock); h256s ret; try { ret = m_watches.at(_watchId).changes; m_watches.at(_watchId).changes.clear(); } catch (...) {} return ret; }
 	virtual h256s watchMessages(unsigned _watchId) override;
 
 	virtual Envelope envelope(h256 _m) const override { try { dev::ReadGuard l(x_messages); return m_messages.at(_m); } catch (...) { return Envelope(); } }
 
+	void cleanup();
+
 private:
 	void streamMessage(h256 _m, RLPStream& _s) const;
 
@@ -67,6 +69,7 @@ private:
 
 	mutable dev::SharedMutex x_messages;
 	std::map<h256, Envelope> m_messages;
+	std::map<unsigned, h256> m_expiryQueue;
 
 	mutable dev::Mutex m_filterLock;
 	std::map<h256, InstalledFilter> m_filters;