diff --git a/test/test-html-build.lua b/test/test-html-build.lua
index ad888b2..8c7818a 100644
--- a/test/test-html-build.lua
+++ b/test/test-html-build.lua
@@ -26,7 +26,7 @@ function TestHTMLBuild.test_empty_root_dtd_systemid()
   local uri = "file:///usr/local/share/test.dtd"
   local document = HTML.build({"html"}, uri)
   luaunit.assertEquals({
-                          ffi.string(document.document.intSubset.SystemID),
+                          ffi.string(document.raw_document.intSubset.SystemID),
                           document:to_html()
                        },
                        {
@@ -43,8 +43,8 @@ function TestHTMLBuild.test_empty_root_dtd_publicid()
   local public_id = "-//W3C//DTD HTML 4.01//EN"
   local document = HTML.build({"html"}, uri, public_id)
   luaunit.assertEquals({
-                         ffi.string(document.document.intSubset.SystemID),
-                         ffi.string(document.document.intSubset.ExternalID),
+                         ffi.string(document.raw_document.intSubset.SystemID),
+                         ffi.string(document.raw_document.intSubset.ExternalID),
                          document:to_html()
                        },
                        {
diff --git a/xmlua/document.lua b/xmlua/document.lua
index f3e43de..016696d 100644
--- a/xmlua/document.lua
+++ b/xmlua/document.lua
@@ -3,7 +3,6 @@ local Document = {}
 local libxml2 = require("xmlua.libxml2")
 local ffi = require("ffi")
 local converter = require("xmlua.converter")
-local to_string = converter.to_string
 
 local Serializable = require("xmlua.serializable")
 local Searchable = require("xmlua.searchable")
@@ -40,11 +39,11 @@ function metatable.__index(document, key)
 end
 
 function methods:root()
-  local root_element = libxml2.xmlDocGetRootElement(self.document)
-  if not root_element then
+  local node = libxml2.xmlDocGetRootElement(self.raw_document)
+  if not node then
     return nil
   end
-  return Element.new(self.document, root_element)
+  return Element.new(self, node)
 end
 
 function methods:parent()
@@ -52,42 +51,42 @@ function methods:parent()
 end
 
 function methods:encoding()
-  return ffi.string(self.document.encoding)
+  return ffi.string(self.raw_document.encoding)
 end
 
 function methods:create_cdata_section(data)
   local raw_cdata_section_node =
-    libxml2.xmlNewCDataBlock(self.document,
+    libxml2.xmlNewCDataBlock(self.raw_document,
                              data,
                              data:len())
-  return CDATASection.new(self.document, raw_cdata_section_node)
+  return CDATASection.new(self, raw_cdata_section_node)
 end
 
 function methods:create_comment(data)
   local raw_comment_node =
     libxml2.xmlNewComment(data)
-  return Comment.new(self.document, raw_comment_node)
+  return Comment.new(self, raw_comment_node)
 end
 
 function methods:create_document_fragment()
   local raw_document_fragment_node =
-    libxml2.xmlNewDocFragment(self.document)
-  return DocumentFragment.new(self.document,
+    libxml2.xmlNewDocFragment(self.raw_document)
+  return DocumentFragment.new(self,
                               raw_document_fragment_node)
 end
 
 function methods:create_document_type(name, external_id, system_id)
   local raw_document_type =
-    libxml2.xmlCreateIntSubset(self.document, name, external_id, system_id)
-  return DocumentType.new(self.document,
+    libxml2.xmlCreateIntSubset(self.raw_document, name, external_id, system_id)
+  return DocumentType.new(self,
                           raw_document_type)
 end
 
 function methods:get_internal_subset()
   local raw_document_type =
-    libxml2.xmlGetIntSubset(self.document)
+    libxml2.xmlGetIntSubset(self.raw_document)
   if raw_document_type ~= nil then
-    return DocumentType.new(self.document,
+    return DocumentType.new(self,
                             raw_document_type)
   else
     return nil
@@ -96,28 +95,28 @@ end
 
 function methods:add_entity_reference(name)
   local raw_entity_reference =
-    libxml2.xmlNewReference(self.document, name)
-  return EntityReference.new(self.document,
+    libxml2.xmlNewReference(self.raw_document, name)
+  return EntityReference.new(self,
                              raw_entity_reference)
 end
 
 function methods:create_namespace(href, prefix)
   local raw_namespace =
     libxml2.xmlNewNs(self.node, href, prefix)
-  return Namespace.new(self.document, raw_namespace)
+  return Namespace.new(self, raw_namespace)
 end
 
 function methods:create_processing_instruction(name, content)
   local raw_processing_instruction =
     libxml2.xmlNewPI(name, content)
-  return ProcessingInstruction.new(self.document,
+  return ProcessingInstruction.new(self,
                              raw_processing_instruction)
 end
 
 function methods:add_entity(entity_info)
   local entity_type_name = entity_info["entity_type"]
   local entity_type = converter.convert_entity_type_name(entity_type_name)
-  local raw_entity = libxml2.xmlAddDocEntity(self.document,
+  local raw_entity = libxml2.xmlAddDocEntity(self.raw_document,
                                              entity_info["name"],
                                              entity_type,
                                              entity_info["external_id"],
@@ -127,14 +126,14 @@ function methods:add_entity(entity_info)
 end
 
 function methods:get_entity(name)
-  local raw_entity = libxml2.xmlGetDocEntity(self.document, name)
+  local raw_entity = libxml2.xmlGetDocEntity(self.raw_document, name)
   return converter.convert_xml_entity(raw_entity)
 end
 
 function methods:add_dtd_entity(entity_info)
   local entity_type_name = entity_info["entity_type"]
   local entity_type = converter.convert_entity_type_name(entity_type_name)
-  local raw_dtd_entity =  libxml2.xmlAddDtdEntity(self.document,
+  local raw_dtd_entity =  libxml2.xmlAddDtdEntity(self.raw_document,
                                               entity_info["name"],
                                               entity_type,
                                               entity_info["external_id"],
@@ -144,7 +143,7 @@ function methods:add_dtd_entity(entity_info)
 end
 
 function methods:get_dtd_entity(name)
-  local raw_dtd_entity = libxml2.xmlGetDtdEntity(self.document, name)
+  local raw_dtd_entity = libxml2.xmlGetDtdEntity(self.raw_document, name)
   return converter.convert_xml_entity(raw_dtd_entity)
 end
 
@@ -167,7 +166,7 @@ function Document.build(raw_document, tree)
 
   local root = Element.build(document, tree[1], tree[2])
   if not libxml2.xmlDocSetRootElement(raw_document, root.node) then
-    root:unlink()
+    --root:unlink()
     return nil
   end
 
@@ -187,7 +186,7 @@ function Document.new(raw_document, errors)
     errors = {}
   end
   local document = {
-    document = raw_document,
+    raw_document = raw_document,
     errors = errors,
   }
   setmetatable(document, metatable)
diff --git a/xmlua/element.lua b/xmlua/element.lua
index 8afebfa..0578252 100644
--- a/xmlua/element.lua
+++ b/xmlua/element.lua
@@ -88,7 +88,7 @@ local function remove_namespace(node, prefix)
     end
   end
 
-  namespace = node.nsDef
+  local namespace = node.nsDef
   local namespace_previous = nil
   while namespace ~= ffi.NULL do
     if is_target_namespace(namespace) then
@@ -127,65 +127,67 @@ local function set_attributes(element, attributes)
   end
 end
 
-local function create_sub_element(document, node, name, attributes)
+local function create_sub_element(document, parent, name, attributes)
   local namespace_prefix, local_name = parse_name(name)
-  local raw_element = libxml2.xmlNewNode(nil, local_name)
-  local element = Element.new(document, raw_element)
+  local node = libxml2.xmlNewNode(nil, local_name)
+  local element = Element.new(document, node)
   set_attributes(element, attributes)
-  local namespace = libxml2.xmlSearchNs(document, raw_element, namespace_prefix)
-  if not namespace and node then
-    namespace = libxml2.xmlSearchNs(document, node, namespace_prefix)
+  local namespace = libxml2.xmlSearchNs(document.raw_document, node, namespace_prefix)
+  if not namespace and parent then
+    namespace = libxml2.xmlSearchNs(document.raw_document, parent, namespace_prefix)
   end
   if namespace then
-    libxml2.xmlSetNs(raw_element, namespace)
+    libxml2.xmlSetNs(node, namespace)
   elseif namespace_prefix then
     element:unlink()
-    raw_element = libxml2.xmlNewNode(nil, name)
-    element = Element.new(document, raw_element)
+    node = libxml2.xmlNewNode(nil, name)
+    element = Element.new(document, node)
     set_attributes(element, attributes)
   end
   return element
 end
 
-function methods:add_child(node)
-  if node.node.parent ~= ffi.NULL then
-    node:unlink()
-  end
-  local raw_added_node =
-    libxml2.xmlAddChild(self.node, node.node)
-  if raw_added_node ~= ffi.NULL then
-    ffi.gc(node.node, nil)
+function methods:add_child(element)
+  local node
+  if self.document == element.document then
+    if element.node.parent ~= ffi.NULL then
+      element:unlink()
+    end
+    node = element.node
+  else
+    node = libxml2.xmlCopyNode(element.node, self.document.raw_document)
   end
+  libxml2.xmlAddChild(self.node, node)
 end
 
-function methods:add_previous_sibling(node)
-  if not self.node and not node.node then
+function methods:add_previous_sibling(element)
+  if not self.node and not element.node then
     error("Already freed receiver node and added node")
   elseif not self.node then
     error("Already freed receiver node")
-  elseif not node.node then
+  elseif not element.node then
     error("Already freed added node")
   end
 
   local raw_added_node, was_freed =
-    libxml2.xmlAddPrevSibling(self.node, node.node)
+    libxml2.xmlAddPrevSibling(self.node, element.node)
   if was_freed then
-    node.node = nil
+    element.node = nil
   end
 end
 
-function methods:append_sibling(node)
-  if not self.node and not node.node then
+function methods:append_sibling(element)
+  if not self.node and not element.node then
     error("Already freed receiver node and appended node")
   elseif not self.node then
     error("Already freed receiver node")
-  elseif not node.node then
+  elseif not element.node then
     error("Already freed appended node")
   end
 
-  local was_freed = libxml2.xmlAddSibling(self.node, node.node)
+  local was_freed = libxml2.xmlAddSibling(self.node, element.node)
   if was_freed then
-    node.node = nil
+    element.node = nil
   end
 end
 
@@ -256,28 +258,28 @@ function methods:insert_element(position, name, attributes)
 end
 
 function methods:unlink()
-  local unlinked_node = Node.unlink(self)
-  return Element.new(nil, unlinked_node)
+  Node.unlink(self)
+  return self
 end
 
 function methods:get_attribute(name)
   local namespace_prefix, local_name = parse_name(name)
   if namespace_prefix == "xmlns" then
-    local namespace = libxml2.xmlSearchNs(self.document, self.node, local_name)
+    local namespace = libxml2.xmlSearchNs(self.document.raw_document, self.node, local_name)
     if namespace then
       return ffi.string(namespace.href)
     else
       return nil
     end
   elseif namespace_prefix == ffi.NULL and local_name == "xmlns" then
-    local namespace = libxml2.xmlSearchNs(self.document, self.node, nil)
+    local namespace = libxml2.xmlSearchNs(self.document.raw_document, self.node, nil)
     if namespace then
       return ffi.string(namespace.href)
     else
       return nil
     end
   elseif namespace_prefix then
-    local namespace = libxml2.xmlSearchNs(self.document,
+    local namespace = libxml2.xmlSearchNs(self.document.raw_document,
                                           self.node,
                                           namespace_prefix)
     if namespace then
@@ -298,7 +300,7 @@ function methods:set_attribute(name, value)
   local namespace_prefix, local_name = parse_name(name)
   local namespace
   if namespace_prefix == "xmlns" then
-    namespace = libxml2.xmlSearchNs(self.document,
+    namespace = libxml2.xmlSearchNs(self.document.raw_document,
                                     self.node,
                                     local_name)
     if namespace then
@@ -308,7 +310,7 @@ function methods:set_attribute(name, value)
       libxml2.xmlNewNs(self.node, value, local_name)
     end
   elseif namespace_prefix == nil and local_name == "xmlns" then
-    namespace = libxml2.xmlSearchNs(self.document, self.node, nil)
+    namespace = libxml2.xmlSearchNs(self.document.raw_document, self.node, nil)
     if namespace then
       libxml2.xmlFree(ffi.cast("void *", namespace.href))
       namespace.href = libxml2.xmlStrdup(value)
@@ -317,7 +319,7 @@ function methods:set_attribute(name, value)
       set_default_namespace(self.node, namespace)
     end
   elseif namespace_prefix then
-    namespace = libxml2.xmlSearchNs(self.document,
+    namespace = libxml2.xmlSearchNs(self.document.raw_document,
                                     self.node,
                                     namespace_prefix)
     if namespace then
@@ -341,7 +343,7 @@ function methods:remove_attribute(name)
   elseif namespace_prefix == nil and local_name == "xmlns" then
     remove_namespace(self.node, nil)
   elseif namespace_prefix then
-    namespace = libxml2.xmlSearchNs(self.document,
+    namespace = libxml2.xmlSearchNs(self.document.raw_document,
                                     self.node,
                                     namespace_prefix)
     if namespace then
@@ -378,12 +380,12 @@ function methods:next()
 end
 
 function methods:root()
-  return Document.new(self.document):root()
+  return self.document:root()
 end
 
 function methods:parent()
   if tonumber(self.node.parent.type) == ffi.C.XML_DOCUMENT_NODE then
-    return Document.new(self.document)
+    return self.document
   else
     return Element.new(self.document, self.node.parent)
   end
@@ -404,7 +406,7 @@ function methods:text()
 end
 
 function methods:namespaces()
-  local raw_namespaces = libxml2.xmlGetNsList(self.document, self.node)
+  local raw_namespaces = libxml2.xmlGetNsList(self.document.raw_document, self.node)
   if not raw_namespaces then
     return nil
   end
@@ -427,23 +429,23 @@ function methods:find_namespace(prefix, href)
   local raw_namespace
   if not prefix and href then
     raw_namespace =
-      libxml2.xmlSearchNsByHref(self.document, self.node, href)
+      libxml2.xmlSearchNsByHref(self.document.raw_document, self.node, href)
   else
     raw_namespace =
-      libxml2.xmlSearchNs(self.document, self.node, prefix)
+      libxml2.xmlSearchNs(self.document.raw_document, self.node, prefix)
   end
   return Namespace.new(self.document, raw_namespace)
 end
 
 -- For internal use
 function Element.build(document, name, attributes)
-  return create_sub_element(document.node, nil, name, attributes)
+  return create_sub_element(document, nil, name, attributes)
 end
 
 function Element.new(document, node)
   local element = {
     document = document,
-    node = node,
+    node = node
   }
   setmetatable(element, metatable)
   return element
diff --git a/xmlua/libxml2.lua b/xmlua/libxml2.lua
index 366b5bd..760638a 100644
--- a/xmlua/libxml2.lua
+++ b/xmlua/libxml2.lua
@@ -16,6 +16,10 @@ require("xmlua.libxml2.xmlsave")
 require("xmlua.libxml2.xpath")
 require("xmlua.libxml2.entities")
 
+local function print_dbg(...)
+  --print(...)
+end
+
 local ffi = require("ffi")
 local loaded, xml2 = pcall(ffi.load, "xml2")
 if not loaded then
@@ -116,7 +120,11 @@ function libxml2.htmlCtxtReadMemory(context, html, options)
   if document == ffi.NULL then
     return nil
   end
-  return ffi.gc(document, libxml2.xmlFreeDoc)
+  print_dbg("htmlCtxtReadMemory: ", document)
+  return ffi.gc(document, function(p)
+    print_dbg("xmlFreeDoc: ", p)
+    xml2.xmlFreeNode(p)
+  end)
 end
 jit.off(libxml2.htmlCtxtReadMemory)
 
@@ -133,7 +141,11 @@ function libxml2.xmlNewParserCtxt()
   if context == ffi.NULL then
     return nil
   end
-  return ffi.gc(context, xml2.xmlFreeParserCtxt)
+  print_dbg("xmlNewParserCtxt: ", context)
+  return ffi.gc(context, function(p)
+    print_dbg("xmlFreeParserCtxt: ", p)
+    xml2.xmlFreeParserCtxt(p)
+  end)
 end
 
 function libxml2.xmlCreatePushParserCtxt(filename)
@@ -197,7 +209,12 @@ function libxml2.xmlCtxtReadMemory(context, xml, options)
   if document == ffi.NULL then
     return nil
   end
-  return ffi.gc(document, libxml2.xmlFreeDoc)
+  print_dbg("xmlCtxtReadMemory: ", document, ", ctx=", context)
+  return ffi.gc(document, function(p)
+    print_dbg("xmlFreeDoc: ", p, ", ctx=", context)
+    xml2.xmlFreeDoc(p)
+  end)
+
 end
 jit.off(libxml2.xmlCtxtReadMemory)
 
@@ -289,7 +306,11 @@ function libxml2.xmlNewDoc(xml_version)
   if document == ffi.NULL then
     return nil
   end
-  return ffi.gc(document, libxml2.xmlFreeDoc)
+  print_dbg("xmlNewDoc: ", document)
+  return ffi.gc(document, function(p)
+    print_dbg("xmlFreeDoc: ", p)
+    xml2.xmlFreeDoc(p)
+  end)
 end
 
 function libxml2.xmlDocSetRootElement(document, root)
@@ -572,10 +593,21 @@ end
 
 function libxml2.xmlUnlinkNode(node)
   xml2.xmlUnlinkNode(node)
-  xml2.xmlSetTreeDoc(node, ffi.NULL)
-  return ffi.gc(node, xml2.xmlFreeNode)
+  print_dbg("xmlUnlinkNode: ", node, ", doc=", node.doc)
+  return ffi.gc(node, function(p)
+    print_dbg("xmlFreeNode: ", p, ", doc=", p.doc)
+    xml2.xmlFreeNode(p)
+  end)
+end
+
+function libxml2.xmlCopyNode(node, doc)
+  return xml2.xmlDocCopyNode(node, doc, 2)
 end
 
+function libxml2.xmlFreeNode(node)
+  print_dbg("xmlFreeNode: ", node, ", doc=", node.doc)
+  xml2.xmlFreeNode(node)
+end
 
 function libxml2.xmlBufferCreate()
   return ffi.gc(xml2.xmlBufferCreate(), xml2.xmlBufferFree)
@@ -643,10 +675,15 @@ function libxml2.xmlXPathEvalExpression(expression, context)
   if object == ffi.NULL then
     return nil
   end
-  return ffi.gc(object, xml2.xmlXPathFreeObject)
+  return object
 end
 jit.off(libxml2.xmlXPathEvalExpression)
 
+function libxml2.xmlXPathFreeObject(object)
+  xml2.xmlXPathFreeObject(object)
+end
+jit.off(libxml2.xmlXPathFreeObject)
+
 function libxml2.xmlXPathRegisterNs(context, prefix, namespace_uri)
   local status = xml2.xmlXPathRegisterNs(context, prefix, namespace_uri)
   return status == 0
diff --git a/xmlua/libxml2/tree.lua b/xmlua/libxml2/tree.lua
index 1c82a77..b2a1491 100644
--- a/xmlua/libxml2/tree.lua
+++ b/xmlua/libxml2/tree.lua
@@ -342,4 +342,5 @@ xmlChar *xmlGetNodePath(const xmlNode *node);
 void xmlFreeNode(xmlNodePtr cur);
 void xmlUnlinkNode(xmlNodePtr cur);
 void xmlSetTreeDoc(xmlNodePtr tree, xmlDocPtr doc);
+xmlNodePtr xmlDocCopyNode(xmlNodePtr node, xmlDocPtr doc, int extended);
 ]]
diff --git a/xmlua/node.lua b/xmlua/node.lua
index 2df258c..68bf24d 100644
--- a/xmlua/node.lua
+++ b/xmlua/node.lua
@@ -36,6 +36,8 @@ function Node:path()
 end
 
 function Node:unlink()
-  return libxml2.xmlUnlinkNode(self.node)
+  libxml2.xmlUnlinkNode(self.node)
+  return self
 end
+
 return Node
diff --git a/xmlua/searchable.lua b/xmlua/searchable.lua
index 0e24b87..922f253 100644
--- a/xmlua/searchable.lua
+++ b/xmlua/searchable.lua
@@ -51,8 +51,9 @@ local ERROR_MESSAGES = {
 }
 
 function Searchable:search(xpath, namespaces)
-  local document = self.document
-  local context = libxml2.xmlXPathNewContext(document)
+  local document = self.document or self
+  local raw_document = document.raw_document
+  local context = libxml2.xmlXPathNewContext(raw_document)
   if not context then
     error("failed to create XPath context")
   end
@@ -96,6 +97,7 @@ function Searchable:search(xpath, namespaces)
   if type == ffi.C.XPATH_NODESET then
     local found_node_set = object.nodesetval
     if found_node_set == ffi.NULL then
+      libxml2.xmlXPathFreeObject(object)
       return NodeSet.new({})
     end
     local raw_node_set = {}
@@ -120,7 +122,10 @@ function Searchable:search(xpath, namespaces)
         -- table.insert(raw_node_set, node)
       end
     end
+    libxml2.xmlXPathFreeObject(object)
     return NodeSet.new(raw_node_set)
+  else
+    libxml2.xmlXPathFreeObject(object)
   end
 end
 
diff --git a/xmlua/serializable.lua b/xmlua/serializable.lua
index bb7fd08..d498924 100644
--- a/xmlua/serializable.lua
+++ b/xmlua/serializable.lua
@@ -17,7 +17,7 @@ local function save(target, flags, failure_message, options)
   if target.node then
     success = libxml2.xmlSaveTree(context, target.node)
   else
-    success = libxml2.xmlSaveDoc(context, target.document)
+    success = libxml2.xmlSaveDoc(context, target.raw_document)
   end
   libxml2.xmlSaveClose(context)
   if not success then
diff --git a/xmlua/xml.lua b/xmlua/xml.lua
index 3b238f0..1f48a74 100644
--- a/xmlua/xml.lua
+++ b/xmlua/xml.lua
@@ -23,7 +23,10 @@ function XML.parse(xml, options)
       error("Failed to parse XML: " .. ffi.string(context.lastError.message))
     end
   end
-  return Document.new(document)
+  local doc = Document.new(document)
+  -- attach context to extend lifetime of dictionaries
+  doc.__context__ = context
+  return doc
 end
 
 return XML