diff --git a/alethzero/MainWin.cpp b/alethzero/MainWin.cpp
index a6ef485df..5d4f9770e 100644
--- a/alethzero/MainWin.cpp
+++ b/alethzero/MainWin.cpp
@@ -263,7 +263,7 @@ unsigned Main::installWatch(LogFilter const& _tf, WatchHandler const& _f)
 
 unsigned Main::installWatch(dev::h256 _tf, WatchHandler const& _f)
 {
-	auto ret = ethereum()->installWatch(_tf);
+	auto ret = ethereum()->installWatch(_tf, Reaping::Manual);
 	m_handlers[ret] = _f;
 	return ret;
 }
diff --git a/libethereum/Client.cpp b/libethereum/Client.cpp
index f46d0d3c9..9d7ecb605 100644
--- a/libethereum/Client.cpp
+++ b/libethereum/Client.cpp
@@ -249,13 +249,13 @@ void Client::clearPending()
 	noteChanged(changeds);
 }
 
-unsigned Client::installWatch(h256 _h)
+unsigned Client::installWatch(h256 _h, Reaping _r)
 {
 	unsigned ret;
 	{
 		Guard l(m_filterLock);
 		ret = m_watches.size() ? m_watches.rbegin()->first + 1 : 0;
-		m_watches[ret] = ClientWatch(_h);
+		m_watches[ret] = ClientWatch(_h, _r);
 		cwatch << "+++" << ret << _h.abridged();
 	}
 	auto ch = logs(ret);
@@ -268,7 +268,7 @@ unsigned Client::installWatch(h256 _h)
 	return ret;
 }
 
-unsigned Client::installWatch(LogFilter const& _f)
+unsigned Client::installWatch(LogFilter const& _f, Reaping _r)
 {
 	h256 h = _f.sha3();
 	{
@@ -279,7 +279,7 @@ unsigned Client::installWatch(LogFilter const& _f)
 			m_filters.insert(make_pair(h, _f));
 		}
 	}
-	return installWatch(h);
+	return installWatch(h, _r);
 }
 
 bool Client::uninstallWatch(unsigned _i)
@@ -692,7 +692,7 @@ void Client::doWork()
 		{
 			Guard l(m_filterLock);
 			for (auto key: keysOf(m_watches))
-				if (chrono::system_clock::now() - m_watches[key].lastPoll > chrono::seconds(20))
+				if (m_watches[key].lastPoll != chrono::system_clock::time_point::max() && chrono::system_clock::now() - m_watches[key].lastPoll > chrono::seconds(20))
 				{
 					toUninstall.push_back(key);
 					cnote << "GC: Uninstall" << key << "(" << chrono::duration_cast<chrono::seconds>(chrono::system_clock::now() - m_watches[key].lastPoll).count() << "s old)";
diff --git a/libethereum/Client.h b/libethereum/Client.h
index 04798ecdb..02d8ef6f8 100644
--- a/libethereum/Client.h
+++ b/libethereum/Client.h
@@ -92,7 +92,7 @@ static const LocalisedLogEntry InitialChange(SpecialLogEntry, 0);
 struct ClientWatch
 {
 	ClientWatch(): lastPoll(std::chrono::system_clock::now()) {}
-	explicit ClientWatch(h256 _id): id(_id), lastPoll(std::chrono::system_clock::now()) {}
+	explicit ClientWatch(h256 _id, Reaping _r): id(_id), lastPoll(_r == Reaping::Automatic ? std::chrono::system_clock::now() : std::chrono::system_clock::time_point::max()) {}
 
 	h256 id;
 	LocalisedLogEntries changes = LocalisedLogEntries{ InitialChange };
@@ -246,8 +246,8 @@ public:
 	virtual bytes codeAt(Address _a, int _block) const;
 	virtual std::map<u256, u256> storageAt(Address _a, int _block) const;
 
-	virtual unsigned installWatch(LogFilter const& _filter) override;
-	virtual unsigned installWatch(h256 _filterId) override;
+	virtual unsigned installWatch(LogFilter const& _filter, Reaping _r = Reaping::Automatic) override;
+	virtual unsigned installWatch(h256 _filterId, Reaping _r = Reaping::Automatic) override;
 	virtual bool uninstallWatch(unsigned _watchId) override;
 	virtual LocalisedLogEntries peekWatch(unsigned _watchId) const;
 	virtual LocalisedLogEntries checkWatch(unsigned _watchId);
diff --git a/libethereum/Interface.h b/libethereum/Interface.h
index 728cb5030..abf7c0a2d 100644
--- a/libethereum/Interface.h
+++ b/libethereum/Interface.h
@@ -39,6 +39,12 @@ namespace eth
 
 using TransactionHashes = h256s;
 
+enum class Reaping
+{
+	Automatic,
+	Manual
+};
+
 /**
  * @brief Main API hub for interfacing with Ethereum.
  */
@@ -92,8 +98,8 @@ public:
 	virtual LocalisedLogEntries logs(LogFilter const& _filter) const = 0;
 
 	/// Install, uninstall and query watches.
-	virtual unsigned installWatch(LogFilter const& _filter) = 0;
-	virtual unsigned installWatch(h256 _filterId) = 0;
+	virtual unsigned installWatch(LogFilter const& _filter, Reaping _r = Reaping::Automatic) = 0;
+	virtual unsigned installWatch(h256 _filterId, Reaping _r = Reaping::Automatic) = 0;
 	virtual bool uninstallWatch(unsigned _watchId) = 0;
 	LocalisedLogEntries peekWatchSafe(unsigned _watchId) const { try { return peekWatch(_watchId); } catch (...) { return LocalisedLogEntries(); } }
 	LocalisedLogEntries checkWatchSafe(unsigned _watchId) { try { return checkWatch(_watchId); } catch (...) { return LocalisedLogEntries(); } }