diff --git a/src/user/user_model.cc b/src/user/user_model.cc
index 77c7289d..bfeed5e8 100644
--- a/src/user/user_model.cc
+++ b/src/user/user_model.cc
@@ -541,6 +541,7 @@ mjCDef* mjCModel::AddDef(string name, int parentid) {
 
   // initialize contents
   if (parentid>=0 && parentid<thisid) {
+    defaults[parentid]->CopyFromSpec();
     *def = *defaults[parentid];
     defaults[parentid]->childid.push_back(thisid);
   }
diff --git a/src/user/user_objects.cc b/src/user/user_objects.cc
index a2895790..71dbcbeb 100644
--- a/src/user/user_objects.cc
+++ b/src/user/user_objects.cc
@@ -566,6 +566,23 @@ void mjCDef::PointToLocal() {
 
 
 
+void mjCDef::CopyFromSpec() {
+  joint.CopyFromSpec();
+  geom.CopyFromSpec();
+  site.CopyFromSpec();
+  camera.CopyFromSpec();
+  light.CopyFromSpec();
+  flex.CopyFromSpec();
+  mesh.CopyFromSpec();
+  material.CopyFromSpec();
+  pair.CopyFromSpec();
+  equality.CopyFromSpec();
+  tendon.CopyFromSpec();
+  actuator.CopyFromSpec();
+}
+
+
+
 //------------------------- class mjCBase implementation -------------------------------------------
 
 // constructor
diff --git a/src/user/user_objects.h b/src/user/user_objects.h
index 17535e33..da7e17e6 100644
--- a/src/user/user_objects.h
+++ b/src/user/user_objects.h
@@ -1397,6 +1397,7 @@ class mjCDef {
   void Compile(const mjCModel* model);     // compiler
   mjCDef& operator=(const mjCDef& other);  // copy assignment
   void PointToLocal(void);
+  void CopyFromSpec(void);
 
   // identifiers
   std::string name;               // class name