diff --git a/iotbx/pdb/hierarchy_atom_bpl.cpp b/iotbx/pdb/hierarchy_atom_bpl.cpp
index 94ed8e5ca4..1523ac0990 100644
--- a/iotbx/pdb/hierarchy_atom_bpl.cpp
+++ b/iotbx/pdb/hierarchy_atom_bpl.cpp
@@ -183,7 +183,7 @@ namespace {
     {
       std::string result = self.format_atom_record(
         0, replace_floats_with);
-      return boost::python::str(result.c_str());
+      return static_cast<boost::python::str>(result);
     }
 
 #ifdef IS_PY3K