diff --git a/pymongo/_cmessagemodule.c b/pymongo/_cmessagemodule.c
index 29c4a7451f..2ae6d79487 100644
--- a/pymongo/_cmessagemodule.c
+++ b/pymongo/_cmessagemodule.c
@@ -762,6 +762,7 @@ static PyObject* _cbson_op_msg(PyObject* self, PyObject* args) {
     Py_XDECREF(iterator);
     buffer_free(buffer);
 bufferfail:
+    PyMem_Free(identifier);
     destroy_codec_options(&options);
     return result;
 }