diff --git a/compiler/cpp/src/thrift/generate/t_php_generator.cc b/compiler/cpp/src/thrift/generate/t_php_generator.cc
index 5e02b9b..8373858 100644
--- a/compiler/cpp/src/thrift/generate/t_php_generator.cc
+++ b/compiler/cpp/src/thrift/generate/t_php_generator.cc
@@ -1285,6 +1285,7 @@
 void t_php_generator::generate_php_struct_json_serialize(ostream& out,
                                                          t_struct* tstruct,
                                                          bool is_result) {
+  indent(out) << "#[\\ReturnTypeWillChange]" << endl;                                                          
   indent(out) << "public function jsonSerialize() {" << endl;
   indent_up();