diff --git a/include/pybind11/eigen/matrix.h b/include/pybind11/eigen/matrix.h
index 5f5ad3867..c21177f05 100644
--- a/include/pybind11/eigen/matrix.h
+++ b/include/pybind11/eigen/matrix.h
@@ -360,6 +360,9 @@ private:
                 return eigen_ref_array<props>(*src);
             case return_value_policy::reference_internal:
                 return eigen_ref_array<props>(*src, parent);
+            case return_value_policy::_return_as_bytes:
+                pybind11_fail("return_value_policy::_return_as_bytes does not apply.");
+                break;
             default:
                 throw cast_error("unhandled return_value_policy: should not happen!");
         };
diff --git a/include/pybind11/eigen/tensor.h b/include/pybind11/eigen/tensor.h
index a823c0f39..343e31b80 100644
--- a/include/pybind11/eigen/tensor.h
+++ b/include/pybind11/eigen/tensor.h
@@ -316,6 +316,10 @@ struct type_caster<Type, typename eigen_tensor_helper<Type>::ValidType> {
                 writeable = !std::is_const<C>::value;
                 break;
 
+            case return_value_policy::_return_as_bytes:
+                pybind11_fail("return_value_policy::_return_as_bytes does not apply.");
+                break;
+
             default:
                 pybind11_fail("pybind11 bug in eigen.h, please file a bug report");
         }