diff --git a/libethereum/Client.cpp b/libethereum/Client.cpp
index 46da3e1f7..cc579ec08 100644
--- a/libethereum/Client.cpp
+++ b/libethereum/Client.cpp
@@ -571,19 +571,13 @@ void Client::doWork()
 {
 	// TODO: Use condition variable rather than this rubbish.
 
-	Guard l(x_fakeSignalSystemState);
-
-	if (m_syncTransactionQueue)
-	{
-		m_syncTransactionQueue = false;
+	bool t = true;
+	if (m_syncTransactionQueue.compare_exchange_strong(t, false))
 		syncTransactionQueue();
-	}
 
-	if (m_syncBlockQueue)
-	{
-		m_syncBlockQueue = false;
+	t = true;
+	if (m_syncBlockQueue.compare_exchange_strong(t, false))
 		syncBlockQueue();
-	}
 
 	checkWatchGarbage();
 
diff --git a/libethereum/Client.h b/libethereum/Client.h
index 16033a11f..289df3fe0 100644
--- a/libethereum/Client.h
+++ b/libethereum/Client.h
@@ -249,10 +249,10 @@ private:
 	void syncTransactionQueue();
 
 	/// Magically called when m_tq needs syncing. Be nice and don't block.
-	void onTransactionQueueReady() { Guard l(x_fakeSignalSystemState); m_syncTransactionQueue = true; }
+	void onTransactionQueueReady() { m_syncTransactionQueue = true; }
 
 	/// Magically called when m_tq needs syncing. Be nice and don't block.
-	void onBlockQueueReady() { Guard l(x_fakeSignalSystemState); m_syncBlockQueue = true; }
+	void onBlockQueueReady() { m_syncBlockQueue = true; }
 
 	/// Called when the post state has changed (i.e. when more transactions are in it or we're mining on a new block).
 	/// This updates m_miningInfo.
@@ -286,9 +286,8 @@ private:
 											///< When did we last both doing GC on the watches?
 
 	// TODO!!!!!! REPLACE WITH A PROPER X-THREAD ASIO SIGNAL SYSTEM (could just be condition variables)
-	mutable Mutex x_fakeSignalSystemState;
-	bool m_syncTransactionQueue = false;
-	bool m_syncBlockQueue = false;
+	std::atomic<bool> m_syncTransactionQueue = {false};
+	std::atomic<bool> m_syncBlockQueue = {false};
 };
 
 }