diff --git a/tests/regression_tests/unstructured_mesh/source_sampling/inputs_true0.dat b/tests/regression_tests/unstructured_mesh/source_sampling/inputs_true0.dat
index dcb56d4033..e50fc71ac4 100644
--- a/tests/regression_tests/unstructured_mesh/source_sampling/inputs_true0.dat
+++ b/tests/regression_tests/unstructured_mesh/source_sampling/inputs_true0.dat
@@ -1125,7 +1125,7 @@
 </geometry>
 <?xml version='1.0' encoding='utf-8'?>
 <materials>
-  <material id="3" name="water">
+  <material id="1" name="water">
     <density units="atom/b-cm" value="0.07416" />
     <nuclide ao="2.0" name="H1" />
     <nuclide ao="1.0" name="O16" />
diff --git a/tests/regression_tests/unstructured_mesh/source_sampling/inputs_true1.dat b/tests/regression_tests/unstructured_mesh/source_sampling/inputs_true1.dat
index 9e22063f14..b416ffb34b 100644
--- a/tests/regression_tests/unstructured_mesh/source_sampling/inputs_true1.dat
+++ b/tests/regression_tests/unstructured_mesh/source_sampling/inputs_true1.dat
@@ -1125,7 +1125,7 @@
 </geometry>
 <?xml version='1.0' encoding='utf-8'?>
 <materials>
-  <material id="3" name="water">
+  <material id="1" name="water">
     <density units="atom/b-cm" value="0.07416" />
     <nuclide ao="2.0" name="H1" />
     <nuclide ao="1.0" name="O16" />