From 093886a4eba866e5b084447ee5993214cc5b6f28 Mon Sep 17 00:00:00 2001
From: Jonathan Shimwell <drshimwell@gmail.com>
Date: Fri, 4 Mar 2022 14:07:16 +0000
Subject: [PATCH] [skip ci] suggestion from review by @Paulromano

Co-authored-by: Paul Romano <paul.k.romano@gmail.com>
---
 openmc/deplete/results_list.py | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/openmc/deplete/results_list.py b/openmc/deplete/results_list.py
index 9ffbe6e730..30ade440c7 100644
--- a/openmc/deplete/results_list.py
+++ b/openmc/deplete/results_list.py
@@ -84,7 +84,8 @@ class ResultsList(list):
         cv.check_value("nuc_units", nuc_units,
                     {"atoms", "atom/b-cm", "atom/cm3"})
 
-        mat_id = str(mat.id)
+        if isinstance(mat, openmc.Material):
+            mat = mat.id
         times = np.empty_like(self, dtype=float)
         concentrations = np.empty_like(self, dtype=float)