diff --git a/libevmasm/Assembly.cpp b/libevmasm/Assembly.cpp
index 42b923df4..0a3bf6b8b 100644
--- a/libevmasm/Assembly.cpp
+++ b/libevmasm/Assembly.cpp
@@ -233,7 +233,7 @@ Json::Value Assembly::streamAsmJson(ostream& _out, StringMap const& _sourceCodes
 {
 	Json::Value root;
 
-	Json::Value collection(Json::arrayValue);
+	Json::Value& collection = root[".code"] = Json::arrayValue;
 	for (AssemblyItem const& i: m_items)
 	{
 		switch (i.type())
@@ -289,11 +289,9 @@ Json::Value Assembly::streamAsmJson(ostream& _out, StringMap const& _sourceCodes
 		}
 	}
 
-	root[".code"] = collection;
-
 	if (!m_data.empty() || !m_subs.empty())
 	{
-		Json::Value data;
+		Json::Value& data = root[".data"] = Json::objectValue;
 		for (auto const& i: m_data)
 			if (u256(i.first) >= m_subs.size())
 				data[toStringInHex((u256)i.first)] = toHex(i.second);
@@ -304,7 +302,6 @@ Json::Value Assembly::streamAsmJson(ostream& _out, StringMap const& _sourceCodes
 			hexStr << hex << i;
 			data[hexStr.str()] = m_subs[i]->stream(_out, "", _sourceCodes, true);
 		}
-		root[".data"] = data;
 	}
 
 	if (m_auxiliaryData.size() > 0)
diff --git a/libsolidity/ast/ASTJsonConverter.cpp b/libsolidity/ast/ASTJsonConverter.cpp
index cb74ea397..f1f6770e3 100644
--- a/libsolidity/ast/ASTJsonConverter.cpp
+++ b/libsolidity/ast/ASTJsonConverter.cpp
@@ -15,8 +15,7 @@
     along with solidity.  If not, see <http://www.gnu.org/licenses/>.
 */
 /**
- * @author Lefteris <lefteris@ethdev.com>
- * @date 2015
+ * @date 2017
  * Converts the AST into json format
  */
 
@@ -81,28 +80,30 @@ void ASTJsonConverter::setJsonNode(
 			(_nodeType == "InlineAssembly") ||
 			(_nodeType == "Throw")
 		)
-		{
-			Json::Value children(Json::arrayValue);
-			m_currentValue["children"] = children;
-		}
+			m_currentValue["children"] = Json::arrayValue;
 
 		for (auto& e: _attributes)
 		{
-			if (
-				(!e.second.isNull()) &&
-					(
-					(e.second.isObject() && e.second.isMember("name")) ||
-					(e.second.isArray() && e.second[0].isObject() && e.second[0].isMember("name")) ||
-					(e.first == "declarations") // (in the case (_,x)= ... there's a nullpointer at [0]
-					)
-			)
+			if ((!e.second.isNull()) && (
+				(e.second.isObject() && e.second.isMember("name")) ||
+				(e.second.isArray() && e.second[0].isObject() && e.second[0].isMember("name")) ||
+				(e.first == "declarations") // (in the case (_,x)= ... there's a nullpointer at [0]
+			))
 			{
 				if (e.second.isObject())
-					m_currentValue["children"].append(std::move(e.second));
+				{
+					if (!m_currentValue["children"].isArray())
+						m_currentValue["children"] = Json::arrayValue;
+					appendMove(m_currentValue["children"], std::move(e.second));
+				}
 				if (e.second.isArray())
 					for (auto& child: e.second)
 						if (!child.isNull())
-							m_currentValue["children"].append(std::move(child));
+						{
+							if (!m_currentValue["children"].isArray())
+								m_currentValue["children"] = Json::arrayValue;
+							appendMove(m_currentValue["children"], std::move(child));
+						}
 			}
 			else
 			{
@@ -147,7 +148,7 @@ Json::Value ASTJsonConverter::typePointerToJson(std::shared_ptr<std::vector<Type
 	{
 		Json::Value arguments(Json::arrayValue);
 		for (auto const& tp: *_tps)
-			arguments.append(typePointerToJson(tp));
+			appendMove(arguments, typePointerToJson(tp));
 		return arguments;
 	}
 	else
@@ -186,7 +187,7 @@ void ASTJsonConverter::print(ostream& _stream, ASTNode const& _node)
 	_stream << toJson(_node);
 }
 
-Json::Value ASTJsonConverter::toJson(ASTNode const& _node)
+Json::Value&& ASTJsonConverter::toJson(ASTNode const& _node)
 {
 	_node.accept(*this);
 	return std::move(m_currentValue);
@@ -543,7 +544,7 @@ bool ASTJsonConverter::visit(VariableDeclarationStatement const& _node)
 {
 	Json::Value varDecs(Json::arrayValue);
 	for (auto const& v: _node.annotation().assignments)
-		varDecs.append(idOrNull(v));
+		appendMove(varDecs, idOrNull(v));
 	setJsonNode(_node, "VariableDeclarationStatement", {
 		make_pair("assignments", std::move(varDecs)),
 		make_pair("declarations", toJson(_node.declarations())),
diff --git a/libsolidity/ast/ASTJsonConverter.h b/libsolidity/ast/ASTJsonConverter.h
index 380ae2c05..60c660c1f 100644
--- a/libsolidity/ast/ASTJsonConverter.h
+++ b/libsolidity/ast/ASTJsonConverter.h
@@ -49,13 +49,16 @@ public:
 	);
 	/// Output the json representation of the AST to _stream.
 	void print(std::ostream& _stream, ASTNode const& _node);
-	Json::Value toJson(ASTNode const& _node);
+	Json::Value&& toJson(ASTNode const& _node);
 	template <class T>
 	Json::Value toJson(std::vector<ASTPointer<T>> const& _nodes)
 	{
 		Json::Value ret(Json::arrayValue);
 		for (auto const& n: _nodes)
-			ret.append(n ? toJson(*n) : Json::nullValue);
+			if (n)
+				appendMove(ret, toJson(*n));
+			else
+				ret.append(Json::nullValue);
 		return ret;
 	}
 	bool visit(SourceUnit const& _node) override;
@@ -154,6 +157,12 @@ private:
 		std::vector<std::pair<std::string, Json::Value>> &_attributes,
 		ExpressionAnnotation const& _annotation
 	);
+	static void appendMove(Json::Value& _array, Json::Value&& _value)
+	{
+		solAssert(_array.isArray(), "");
+		_array.append(std::move(_value));
+	}
+
 	bool m_legacy = false; ///< if true, use legacy format
 	bool m_inEvent = false; ///< whether we are currently inside an event or not
 	Json::Value m_currentValue;
diff --git a/solc/CommandLineInterface.cpp b/solc/CommandLineInterface.cpp
index 152526f4e..bfc53aef5 100644
--- a/solc/CommandLineInterface.cpp
+++ b/solc/CommandLineInterface.cpp
@@ -851,7 +851,7 @@ void CommandLineInterface::handleCombinedJSON()
 		output[g_strContracts] = Json::Value(Json::objectValue);
 	for (string const& contractName: contracts)
 	{
-		Json::Value contractData(Json::objectValue);
+		Json::Value& contractData = output[g_strContracts][contractName] = Json::objectValue;
 		if (requests.count(g_strAbi))
 			contractData[g_strAbi] = dev::jsonCompactPrint(m_compiler->contractABI(contractName));
 		if (requests.count("metadata"))
@@ -885,7 +885,6 @@ void CommandLineInterface::handleCombinedJSON()
 			contractData[g_strNatspecDev] = dev::jsonCompactPrint(m_compiler->natspecDev(contractName));
 		if (requests.count(g_strNatspecUser))
 			contractData[g_strNatspecUser] = dev::jsonCompactPrint(m_compiler->natspecUser(contractName));
-		output[g_strContracts][contractName] = contractData;
 	}
 
 	bool needsSourceList = requests.count(g_strAst) || requests.count(g_strSrcMap) || requests.count(g_strSrcMapRuntime);