diff --git a/libdevcore/Common.h b/libdevcore/Common.h
index b7eca90f6..ce637a2a6 100644
--- a/libdevcore/Common.h
+++ b/libdevcore/Common.h
@@ -92,7 +92,15 @@ public:
 	explicit secure_vector(vector_ref<const T> _c): m_data(_c.data(), _c.data() + _c.size()) {}
 	~secure_vector() { ref().cleanse(); }
 
-	secure_vector<T>& operator=(secure_vector<T> const& _c) { ref().cleanse(); m_data = _c.m_data; return *this; }
+	secure_vector<T>& operator=(secure_vector<T> const& _c)
+	{
+		if (&_c == this)
+			return *this;
+
+		ref().cleanse();
+		m_data = _c.m_data;
+		return *this;
+	}
 	std::vector<T>& writable() { clear(); return m_data; }
 	std::vector<T> const& makeInsecure() const { return m_data; }
 
diff --git a/libdevcore/Worker.h b/libdevcore/Worker.h
index fbc4d7042..23c90ab78 100644
--- a/libdevcore/Worker.h
+++ b/libdevcore/Worker.h
@@ -54,7 +54,12 @@ protected:
 	Worker(Worker&& _m) { std::swap(m_name, _m.m_name); }
 
 	/// Move-assignment.
-	Worker& operator=(Worker&& _m) { std::swap(m_name, _m.m_name); return *this; }
+	Worker& operator=(Worker&& _m)
+	{
+		assert(&_m != this);
+		std::swap(m_name, _m.m_name);
+		return *this;
+	}
 
 	virtual ~Worker() { terminate(); }
 
diff --git a/libethereum/Block.cpp b/libethereum/Block.cpp
index a57ded73d..1c8dc1b21 100644
--- a/libethereum/Block.cpp
+++ b/libethereum/Block.cpp
@@ -80,6 +80,9 @@ Block::Block(Block const& _s):
 
 Block& Block::operator=(Block const& _s)
 {
+	if (&_s == this)
+		return *this;
+
 	m_state = _s.m_state;
 	m_transactions = _s.m_transactions;
 	m_receipts = _s.m_receipts;
diff --git a/libethereum/State.cpp b/libethereum/State.cpp
index bd5feacb0..5258e0668 100644
--- a/libethereum/State.cpp
+++ b/libethereum/State.cpp
@@ -136,6 +136,9 @@ void State::paranoia(std::string const& _when, bool _enforceRefs) const
 
 State& State::operator=(State const& _s)
 {
+	if (&_s == this)
+		return *this;
+
 	m_db = _s.m_db;
 	m_state.open(&m_db, _s.m_state.root(), Verification::Skip);
 	m_cache = _s.m_cache;
diff --git a/libethereum/TransactionQueue.cpp b/libethereum/TransactionQueue.cpp
index aeeb35214..bf8e14a27 100644
--- a/libethereum/TransactionQueue.cpp
+++ b/libethereum/TransactionQueue.cpp
@@ -402,4 +402,3 @@ void TransactionQueue::verifierBody()
 		}
 	}
 }
-
diff --git a/libethereum/TransactionQueue.h b/libethereum/TransactionQueue.h
index 9c8283aa2..b7af75013 100644
--- a/libethereum/TransactionQueue.h
+++ b/libethereum/TransactionQueue.h
@@ -140,7 +140,14 @@ private:
 		UnverifiedTransaction() {}
 		UnverifiedTransaction(bytesConstRef const& _t, h512 const& _nodeId): transaction(_t.toBytes()), nodeId(_nodeId) {}
 		UnverifiedTransaction(UnverifiedTransaction&& _t): transaction(std::move(_t.transaction)) {}
-		UnverifiedTransaction& operator=(UnverifiedTransaction&& _other) { transaction = std::move(_other.transaction); nodeId = std::move(_other.nodeId); return *this; }
+		UnverifiedTransaction& operator=(UnverifiedTransaction&& _other)
+		{
+			assert(&_other != this);
+
+			transaction = std::move(_other.transaction);
+			nodeId = std::move(_other.nodeId);
+			return *this;
+		}
 
 		UnverifiedTransaction(UnverifiedTransaction const&) = delete;
 		UnverifiedTransaction& operator=(UnverifiedTransaction const&) = delete;
diff --git a/libethereum/VerifiedBlock.h b/libethereum/VerifiedBlock.h
index 8bac12f90..fb96c084c 100644
--- a/libethereum/VerifiedBlock.h
+++ b/libethereum/VerifiedBlock.h
@@ -58,6 +58,8 @@ struct VerifiedBlock
 
 	VerifiedBlock& operator=(VerifiedBlock&& _other)
 	{
+		assert(&_other != this);
+
 		verified = (std::move(_other.verified));
 		blockData = (std::move(_other.blockData));
 		return *this;
diff --git a/libevmasm/SourceLocation.h b/libevmasm/SourceLocation.h
index 35e3c0318..b8b57b609 100644
--- a/libevmasm/SourceLocation.h
+++ b/libevmasm/SourceLocation.h
@@ -41,8 +41,21 @@ struct SourceLocation
 	SourceLocation(): start(-1), end(-1) { }
 
 	SourceLocation(SourceLocation const& _other):
-		start(_other.start), end(_other.end), sourceName(_other.sourceName) {}
-	SourceLocation& operator=(SourceLocation const& _other) { start = _other.start; end = _other.end; sourceName = _other.sourceName; return *this;}
+		start(_other.start),
+		end(_other.end),
+		sourceName(_other.sourceName)
+	{}
+
+	SourceLocation& operator=(SourceLocation const& _other)
+	{
+		if (&_other == this)
+			return *this;
+
+		start = _other.start;
+		end = _other.end;
+		sourceName = _other.sourceName;
+		return *this;
+	}
 
 	bool operator==(SourceLocation const& _other) const { return start == _other.start && end == _other.end;}
 	bool operator!=(SourceLocation const& _other) const { return !operator==(_other); }
diff --git a/libp2p/Common.h b/libp2p/Common.h
index e6411ce67..9caa9c4c7 100644
--- a/libp2p/Common.h
+++ b/libp2p/Common.h
@@ -224,7 +224,13 @@ class DeadlineOps
 		~DeadlineOp() {}
 		
 		DeadlineOp(DeadlineOp&& _s): m_timer(_s.m_timer.release()) {}
-		DeadlineOp& operator=(DeadlineOp&& _s) { m_timer.reset(_s.m_timer.release()); return *this; }
+		DeadlineOp& operator=(DeadlineOp&& _s)
+		{
+			assert(&_s != this);
+
+			m_timer.reset(_s.m_timer.release());
+			return *this;
+		}
 		
 		bool expired() { Guard l(x_timer); return m_timer->expires_from_now().total_nanoseconds() <= 0; }
 		void wait() { Guard l(x_timer); m_timer->wait(); }
diff --git a/libsolidity/Types.cpp b/libsolidity/Types.cpp
index 744362fb7..6a8d33dcd 100644
--- a/libsolidity/Types.cpp
+++ b/libsolidity/Types.cpp
@@ -79,6 +79,8 @@ pair<u256, unsigned> const* StorageOffsets::getOffset(size_t _index) const
 
 MemberList& MemberList::operator=(MemberList&& _other)
 {
+	assert(&_other != this);
+
 	m_memberTypes = std::move(_other.m_memberTypes);
 	m_storageOffsets = std::move(_other.m_storageOffsets);
 	return *this;