diff --git a/src/user/user_model.cc b/src/user/user_model.cc
index 50f37bf8..c1b1b3ae 100644
--- a/src/user/user_model.cc
+++ b/src/user/user_model.cc
@@ -1072,6 +1072,14 @@ void mjCModel::DeleteAll<mjCTexture>(std::vector<mjCTexture*>& elements) {
   elements.clear();
 }
 
+template <>
+void mjCModel::DeleteAll<mjCKey>(std::vector<mjCKey*>& elements) {
+  for (mjCKey* element : elements) {
+    delete element;
+  }
+  elements.clear();
+}
+
 // set nuser fields
 void mjCModel::SetNuser() {
   if (nuser_body == -1) {
diff --git a/src/user/user_objects.cc b/src/user/user_objects.cc
index 4260da3c..6cbfa6e4 100644
--- a/src/user/user_objects.cc
+++ b/src/user/user_objects.cc
@@ -860,6 +860,9 @@ mjCBody& mjCBody::operator+=(const mjCFrame& other) {
   // attach referencing elements
   *model += *other.model;
 
+  // (b/350784262) delete keyframes
+  model->DeleteAll<mjCKey>(model->keys_);
+
   // clear namespace and return body
   other.model->prefix.clear();
   other.model->suffix.clear();
@@ -1598,6 +1601,9 @@ mjCFrame& mjCFrame::operator+=(const mjCBody& other) {
   // attach referencing elements
   *model += *other.model;
 
+  // (b/350784262) delete keyframes
+  model->DeleteAll<mjCKey>(model->keys_);
+
   // clear suffixes and return
   other.model->suffix.clear();
   other.model->prefix.clear();