diff --git a/arangod/Aql/AstNode.cpp b/arangod/Aql/AstNode.cpp
index eba0764b20..8e63527a92 100644
--- a/arangod/Aql/AstNode.cpp
+++ b/arangod/Aql/AstNode.cpp
@@ -92,7 +92,7 @@ void AstNode::toJson (TRI_json_t* json,
         TRI_Insert3ArrayJson(zone, node, "value", TRI_CreateStringCopyJson(zone, "null"));
         break;
       case VALUE_TYPE_BOOL:
-        TRI_Insert3ArrayJson(zone, node, "value", TRI_CreateStringCopyJson(zone, value.value._bool ? "true" : "false"));
+        TRI_Insert3ArrayJson(zone, node, "value", TRI_CreateBooleanJson(zone, value.value._bool));
         break;
       case VALUE_TYPE_INT:
         TRI_Insert3ArrayJson(zone, node, "value", TRI_CreateNumberJson(zone, static_cast<double>(value.value._int)));
diff --git a/arangod/Aql/Parser.cpp b/arangod/Aql/Parser.cpp
index 446ec3f1dc..bf501943c8 100644
--- a/arangod/Aql/Parser.cpp
+++ b/arangod/Aql/Parser.cpp
@@ -49,7 +49,6 @@ Parser::Parser (Query* query)
     _remainingLength(query->queryLength()),
     _offset(0),
     _marker(nullptr),
-    _subQueryCount(0),
     _uniqueId(0),
     _stack() {
   
@@ -87,7 +86,7 @@ bool Parser::configureWriteQuery (QueryType type,
   TRI_ASSERT(type != AQL_QUERY_READ);
 
   // check if we currently are in a subquery
-  if (isInSubQuery()) {
+  if (_ast->isInSubQuery()) {
     // data modification not allowed in sub-queries
     registerError(TRI_ERROR_QUERY_MODIFY_IN_SUBQUERY);
     return false;
diff --git a/arangod/Aql/Parser.h b/arangod/Aql/Parser.h
index 83151cf3f3..15d90cdb7a 100644
--- a/arangod/Aql/Parser.h
+++ b/arangod/Aql/Parser.h
@@ -117,31 +117,6 @@ namespace triagens {
           return _ast;
         }
 
-////////////////////////////////////////////////////////////////////////////////
-/// @brief start a subquery
-////////////////////////////////////////////////////////////////////////////////
-
-        inline void startSubQuery () {
-          ++_subQueryCount;
-        }
-
-////////////////////////////////////////////////////////////////////////////////
-/// @brief end a subquery
-////////////////////////////////////////////////////////////////////////////////
-        
-        inline void endSubQuery () {
-          TRI_ASSERT(_subQueryCount > 0);
-          --_subQueryCount;
-        }
-
-////////////////////////////////////////////////////////////////////////////////
-/// @brief whether or not we are in a subquery
-////////////////////////////////////////////////////////////////////////////////
-
-        inline bool isInSubQuery () const {
-          return (_subQueryCount > 0);
-        }
-
 ////////////////////////////////////////////////////////////////////////////////
 /// @brief return the scanner
 ////////////////////////////////////////////////////////////////////////////////
@@ -290,7 +265,6 @@ namespace triagens {
         size_t        _offset;          // current parse position
         char const*   _marker;          // a position used temporarily during parsing
 
-        size_t        _subQueryCount;   // number of active subqueries
         size_t        _uniqueId;        // a counter to generate unique (temporary) variable names
 
 
diff --git a/arangod/Aql/QueryAst.cpp b/arangod/Aql/QueryAst.cpp
index 1175d60819..c505a8f5e0 100644
--- a/arangod/Aql/QueryAst.cpp
+++ b/arangod/Aql/QueryAst.cpp
@@ -64,6 +64,7 @@ QueryAst::QueryAst (Query* query,
     _bindParameters(),
     _collectionNames(),
     _root(nullptr),
+    _queries(),
     _writeCollection(nullptr),
     _writeOptions(nullptr) {
 
@@ -71,7 +72,11 @@ QueryAst::QueryAst (Query* query,
   TRI_ASSERT(_parser != nullptr);
 
   _nodes.reserve(32);
-  _root = createNode(NODE_TYPE_ROOT);
+  _strings.reserve(32);
+
+  startSubQuery();
+
+  TRI_ASSERT(_root != nullptr);
 }
 
 ////////////////////////////////////////////////////////////////////////////////
@@ -496,14 +501,16 @@ AstNode* QueryAst::createNodeTernaryOperator (AstNode const* condition,
 /// @brief create an AST subquery node
 ////////////////////////////////////////////////////////////////////////////////
 
-AstNode* QueryAst::createNodeSubquery (char const* tempName) {
-  if (tempName == nullptr) {
+AstNode* QueryAst::createNodeSubquery (char const* variableName,
+                                       AstNode const* subQuery) {
+  if (variableName == nullptr) {
     THROW_ARANGO_EXCEPTION(TRI_ERROR_OUT_OF_MEMORY);
   }
 
   AstNode* node = createNode(NODE_TYPE_SUBQUERY);
-  AstNode* variable = createNodeVariable(tempName, false);
+  AstNode* variable = createNodeVariable(variableName, false);
   node->addMember(variable);
+  node->addMember(subQuery);
 
   return node;
 }
diff --git a/arangod/Aql/QueryAst.h b/arangod/Aql/QueryAst.h
index fdb2caefe5..c51dda5427 100644
--- a/arangod/Aql/QueryAst.h
+++ b/arangod/Aql/QueryAst.h
@@ -87,6 +87,57 @@ namespace triagens {
 
       public:
 
+////////////////////////////////////////////////////////////////////////////////
+/// @brief begin a subquery
+////////////////////////////////////////////////////////////////////////////////
+
+        void startSubQuery () {
+          // insert a new root node
+          AstNodeType type;
+
+          if (_queries.empty()) {
+            // root node of query
+            type = NODE_TYPE_ROOT;
+          }
+          else {
+            // sub query node
+            type = NODE_TYPE_SUBQUERY;
+          }
+
+          auto root = createNode(type);
+
+          // save the root node
+          _queries.push_back(root);
+
+          // set the current root node if everything went well
+          _root = root;
+        }
+
+////////////////////////////////////////////////////////////////////////////////
+/// @brief end a subquery
+////////////////////////////////////////////////////////////////////////////////
+
+        AstNode* endSubQuery () {
+          // get the current root node
+          AstNode* root = _queries.back();
+          // remove it from the stack
+          _queries.pop_back();
+
+          // set root node to previous root node
+          _root = _queries.back();
+
+          // return the root node we just popped from the stack
+          return root;
+        }
+
+////////////////////////////////////////////////////////////////////////////////
+/// @brief whether or not we currently are in a subquery
+////////////////////////////////////////////////////////////////////////////////
+
+        bool isInSubQuery () const {
+          return (_queries.size() > 1);
+        }
+
 ////////////////////////////////////////////////////////////////////////////////
 /// @brief return a copy of our own bind parameters
 ////////////////////////////////////////////////////////////////////////////////
@@ -297,7 +348,8 @@ namespace triagens {
 /// @brief create an AST subquery node
 ////////////////////////////////////////////////////////////////////////////////
 
-        AstNode* createNodeSubquery (char const*);
+        AstNode* createNodeSubquery (char const*,
+                                     AstNode const*);
 
 ////////////////////////////////////////////////////////////////////////////////
 /// @brief create an AST attribute access node
@@ -563,6 +615,12 @@ namespace triagens {
 
         AstNode*                         _root;
 
+////////////////////////////////////////////////////////////////////////////////
+/// @brief root nodes of queries and subqueries
+////////////////////////////////////////////////////////////////////////////////
+
+        std::vector<AstNode*>            _queries;
+
 ////////////////////////////////////////////////////////////////////////////////
 /// @brief which collection is going to be modified in the query 
 ////////////////////////////////////////////////////////////////////////////////
diff --git a/arangod/Aql/grammar.y b/arangod/Aql/grammar.y
index 590b273225..bfe1a5488c 100644
--- a/arangod/Aql/grammar.y
+++ b/arangod/Aql/grammar.y
@@ -434,16 +434,16 @@ expression:
     }
   | T_OPEN {
       parser->ast()->scopes()->start(triagens::aql::AQL_SCOPE_SUBQUERY);
-      parser->startSubQuery();
+      parser->ast()->startSubQuery();
     } query T_CLOSE {
-      parser->endSubQuery();
+      AstNode* node = parser->ast()->endSubQuery();
       parser->ast()->scopes()->endCurrent();
 
-      char const* tempName = parser->generateName();
-      auto subQuery = parser->ast()->createNodeSubquery(tempName);
+      char const* variableName = parser->generateName();
+      auto subQuery = parser->ast()->createNodeLet(variableName, node, false);
       parser->ast()->addOperation(subQuery);
 
-      $$ = parser->ast()->createNodeReference(tempName);
+      $$ = parser->ast()->createNodeReference(variableName);
     } 
   | operator_unary {
       $$ = $1;