diff --git a/include/pybind11/cast.h b/include/pybind11/cast.h
index c1d0bbc..4901ea3 100644
--- a/include/pybind11/cast.h
+++ b/include/pybind11/cast.h
@@ -458,7 +458,7 @@
     auto &instances = get_internals().registered_instances;
     auto range = instances.equal_range(ptr);
     for (auto it = range.first; it != range.second; ++it) {
-        for (auto vh : values_and_holders(it->second)) {
+        for (const auto &vh : values_and_holders(it->second)) {
             if (vh.type == type)
                 return handle((PyObject *) it->second);
         }
diff --git a/include/pybind11/detail/class.h b/include/pybind11/detail/class.h
index d58f04e..8d36744 100644
--- a/include/pybind11/detail/class.h
+++ b/include/pybind11/detail/class.h
@@ -169,7 +169,7 @@
     auto instance = reinterpret_cast<detail::instance *>(self);
 
     // Ensure that the base __init__ function(s) were called
-    for (auto vh : values_and_holders(instance)) {
+    for (const auto &vh : values_and_holders(instance)) {
         if (!vh.holder_constructed()) {
             PyErr_Format(PyExc_TypeError, "%.200s.__init__() must be called when overriding __init__",
                          vh.type->type->tp_name);