diff --git a/doc/includes/references.h b/doc/includes/references.h
index c6c06f5c..15345e99 100644
--- a/doc/includes/references.h
+++ b/doc/includes/references.h
@@ -3542,7 +3542,7 @@ mjsText* mjs_addText(mjSpec* s);
 mjsTuple* mjs_addTuple(mjSpec* s);
 mjsKey* mjs_addKey(mjSpec* s);
 mjsPlugin* mjs_addPlugin(mjSpec* s);
-mjsDefault* mjs_addDefault(mjSpec* s, const char* classname, int parentid, int* id);
+mjsDefault* mjs_addDefault(mjSpec* s, const char* classname, const mjsDefault* parent);
 mjsMesh* mjs_addMesh(mjSpec* s, mjsDefault* def);
 mjsHField* mjs_addHField(mjSpec* s);
 mjsSkin* mjs_addSkin(mjSpec* s);
diff --git a/include/mujoco/mujoco.h b/include/mujoco/mujoco.h
index 6cb6f7e5..4a45bc72 100644
--- a/include/mujoco/mujoco.h
+++ b/include/mujoco/mujoco.h
@@ -1492,7 +1492,7 @@ MJAPI mjsKey* mjs_addKey(mjSpec* s);
 MJAPI mjsPlugin* mjs_addPlugin(mjSpec* s);
 
 // Add default.
-MJAPI mjsDefault* mjs_addDefault(mjSpec* s, const char* classname, int parentid, int* id);
+MJAPI mjsDefault* mjs_addDefault(mjSpec* s, const char* classname, const mjsDefault* parent);
 
 
 //---------------------------------- Assets --------------------------------------------------------
diff --git a/introspect/functions.py b/introspect/functions.py
index 58985da5..a4808e53 100644
--- a/introspect/functions.py
+++ b/introspect/functions.py
@@ -9499,13 +9499,9 @@ FUNCTIONS: Mapping[str, FunctionDecl] = dict([
                  ),
              ),
              FunctionParameterDecl(
-                 name='parentid',
-                 type=ValueType(name='int'),
-             ),
-             FunctionParameterDecl(
-                 name='id',
+                 name='parent',
                  type=PointerType(
-                     inner_type=ValueType(name='int'),
+                     inner_type=ValueType(name='mjsDefault', is_const=True),
                  ),
              ),
          ),
diff --git a/src/user/user_api.cc b/src/user/user_api.cc
index de3e58af..f71fa176 100644
--- a/src/user/user_api.cc
+++ b/src/user/user_api.cc
@@ -437,10 +437,11 @@ mjsPlugin* mjs_addPlugin(mjSpec* s) {
 
 
 // add default to model
-mjsDefault* mjs_addDefault(mjSpec* s, const char* classname, int parentid, int* id) {
+mjsDefault* mjs_addDefault(mjSpec* s, const char* classname, const mjsDefault* parent) {
   mjCModel* modelC = static_cast<mjCModel*>(s->element);
-  *id = (int)modelC->NumDefaults();
-  mjCDef* def = modelC->AddDefault(classname, parentid);
+  mjCDef* parentC = parent ? static_cast<mjCDef*>(parent->element) :
+                             static_cast<mjCModel*>(s->element)->Defaults(0);
+  mjCDef* def = modelC->AddDefault(classname, parentC);
   if (def) {
     return &def->spec;
   } else {
diff --git a/src/user/user_api.h b/src/user/user_api.h
index 168ae6d2..9e30b105 100644
--- a/src/user/user_api.h
+++ b/src/user/user_api.h
@@ -156,7 +156,7 @@ MJAPI mjsKey* mjs_addKey(mjSpec* s);
 MJAPI mjsPlugin* mjs_addPlugin(mjSpec* s);
 
 // Add default.
-MJAPI mjsDefault* mjs_addDefault(mjSpec* s, const char* classname, int parentid, int* id);
+MJAPI mjsDefault* mjs_addDefault(mjSpec* s, const char* classname, const mjsDefault* parent);
 
 
 //---------------------------------- Add assets ----------------------------------------------------
diff --git a/src/user/user_model.cc b/src/user/user_model.cc
index 23f94634..0fadddd0 100644
--- a/src/user/user_model.cc
+++ b/src/user/user_model.cc
@@ -741,7 +741,9 @@ mjCDef* mjCModel::FindDefault(string name) {
 
 
 // add default class to array
-mjCDef* mjCModel::AddDefault(string name, int parentid) {
+mjCDef* mjCModel::AddDefault(string name, mjCDef* parent) {
+  int parentid = parent ? parent->id : 0;
+
   // check for repeated name
   int thisid = (int)defaults_.size();
   for (int i=0; i<thisid; i++) {
@@ -753,6 +755,7 @@ mjCDef* mjCModel::AddDefault(string name, int parentid) {
   // create new object
   mjCDef* def = new mjCDef;
   defaults_.push_back(def);
+  def->id = thisid;
 
   // initialize contents
   if (parentid>=0 && parentid<thisid) {
diff --git a/src/user/user_model.h b/src/user/user_model.h
index 5d2ee204..95adb202 100644
--- a/src/user/user_model.h
+++ b/src/user/user_model.h
@@ -205,15 +205,15 @@ class mjCModel : public mjCModel_, private mjSpec {
   mjCBase* GetObject(mjtObj type, int id);  // pointer to specified object
 
   // API for access to other variables
-  bool IsCompiled() const;                                       // is model already compiled
-  const mjCError& GetError() const;                              // get reference of error object
-  mjCBody* GetWorld();                                           // pointer to world body
-  mjCDef* FindDefault(std::string name);                         // find defaults class name
-  mjCDef* AddDefault(std::string name, int parentid);            // add defaults class to array
-  mjCBase* FindObject(mjtObj type, std::string name) const;      // find object given type and name
-  mjCBody* FindBody(mjCBody* body, std::string name);            // find body given name
-  mjCFrame* FindFrame(mjCBody* body, std::string name) const;    // find frame given name
-  bool IsNullPose(const mjtNum* pos, const mjtNum* quat) const;  // detect null pose
+  bool IsCompiled() const;                                         // is model already compiled
+  const mjCError& GetError() const;                                // get reference of error object
+  mjCBody* GetWorld();                                             // pointer to world body
+  mjCDef* FindDefault(std::string name);                           // find defaults class name
+  mjCDef* AddDefault(std::string name, mjCDef* parent = nullptr);  // add defaults class to array
+  mjCBase* FindObject(mjtObj type, std::string name) const;        // find object given type and name
+  mjCBody* FindBody(mjCBody* body, std::string name);              // find body given name
+  mjCFrame* FindFrame(mjCBody* body, std::string name) const;      // find frame given name
+  bool IsNullPose(const mjtNum* pos, const mjtNum* quat) const;    // detect null pose
   void SetActivePlugins(const std::vector<std::pair<const mjpPlugin*, int>>&& active_plugins) {
     active_plugins_ = std::move(active_plugins);
   }
diff --git a/src/user/user_objects.cc b/src/user/user_objects.cc
index 68fb0a92..4f10402a 100644
--- a/src/user/user_objects.cc
+++ b/src/user/user_objects.cc
@@ -517,6 +517,7 @@ int mjCBoundingVolumeHierarchy::MakeBVH(
 // constructor
 mjCDef::mjCDef() {
   name.clear();
+  id = 0;
   parentid = -1;
   childid.clear();
   mjs_defaultJoint(&joint_.spec);
diff --git a/src/user/user_objects.h b/src/user/user_objects.h
index 4e1b8a9f..9c50b483 100644
--- a/src/user/user_objects.h
+++ b/src/user/user_objects.h
@@ -1651,6 +1651,7 @@ class mjCDef : public mjsElement {
 
   // identifiers
   std::string name;               // class name
+  int id;                         // id of this default
   int parentid;                   // id of parent class
   std::vector<int> childid;       // ids of child classes
 
diff --git a/src/xml/xml_native_reader.cc b/src/xml/xml_native_reader.cc
index 250f2bfe..6e685c76 100644
--- a/src/xml/xml_native_reader.cc
+++ b/src/xml/xml_native_reader.cc
@@ -29,6 +29,7 @@
 
 #include "tinyxml2.h"
 
+#include <mujoco/mujoco.h>
 #include <mujoco/mjmodel.h>
 #include <mujoco/mjplugin.h>
 #include <mujoco/mjtnum.h>
@@ -862,7 +863,7 @@ void mjXReader::Parse(XMLElement* root) {
   readingdefaults = true;
   for (XMLElement* section = FirstChildElement(root, "default"); section;
        section = NextSiblingElement(section, "default")) {
-    Default(section, -1);
+    Default(section, nullptr);
   }
   readingdefaults = false;
 
@@ -2667,27 +2668,24 @@ void mjXReader::OnePlugin(XMLElement* elem, mjsPlugin* plugin) {
 //------------------ MJCF-specific sections --------------------------------------------------------
 
 // default section parser
-void mjXReader::Default(XMLElement* section, int parentid) {
+void mjXReader::Default(XMLElement* section, const mjsDefault* def) {
   XMLElement* elem;
   string text, name;
-  mjsDefault* def;
-  int thisid;
 
   // create new default, except at top level (already added in mjCModel constructor)
   text.clear();
   ReadAttrTxt(section, "class", text);
   if (text.empty()) {
-    if (parentid >= 0) {
+    if (def) {
       throw mjXError(section, "empty class name");
     }
   }
-  if (parentid >= 0) {
-    def = mjs_addDefault(model, text.c_str(), parentid, &thisid);
+  if (def) {
+    def = mjs_addDefault(model, text.c_str(), def);
     if (!def) {
       throw mjXError(section, "repeated default class name");
     }
   } else {
-    thisid = 0;
     def = mjs_getSpecDefault(model);
     if (!text.empty() && text != "main") {
       throw mjXError(section, "top-level default class 'main' cannot be renamed");
@@ -2755,7 +2753,7 @@ void mjXReader::Default(XMLElement* section, int parentid) {
 
     // read default
     if (name=="default") {
-      Default(elem, thisid);
+      Default(elem, def);
     }
 
     // advance
diff --git a/src/xml/xml_native_reader.h b/src/xml/xml_native_reader.h
index aa20841a..f2049bec 100644
--- a/src/xml/xml_native_reader.h
+++ b/src/xml/xml_native_reader.h
@@ -48,7 +48,7 @@ class mjXReader : public mjXBase {
 
  private:
   // XML section specific to MJCF
-  void Default(tinyxml2::XMLElement* section,   int parentid);         // default section
+  void Default(tinyxml2::XMLElement* section, const mjsDefault* def);  // default section
   void Extension(tinyxml2::XMLElement* section);                       // extension section
   void Custom(tinyxml2::XMLElement* section);                          // custom section
   void Visual(tinyxml2::XMLElement* section);                          // visual section