diff --git a/scripts/openmc-update-inputs b/scripts/openmc-update-inputs
index 0d25b5b974..3b4e9a3595 100755
--- a/scripts/openmc-update-inputs
+++ b/scripts/openmc-update-inputs
@@ -298,4 +298,4 @@ if __name__ == '__main__':
             move(fname, fname + '.original')
 
             # Write a new geometry file.
-            tree.write(fname)
+            tree.write(fname, xml_declaration=True)
diff --git a/src/mesh.cpp b/src/mesh.cpp
index 590df53e17..915679dd3d 100644
--- a/src/mesh.cpp
+++ b/src/mesh.cpp
@@ -149,8 +149,10 @@ RegularMesh::RegularMesh(pugi::xml_node node)
         "the <lower_left> coordinates on a tally mesh.");
     }
 
-    // Set width and upper right coordinate
-    width_ = xt::eval((upper_right_ - lower_left_) / shape_);
+    // Set width
+    if (shape_.size() > 0) {
+      width_ = xt::eval((upper_right_ - lower_left_) / shape_);
+    }
   } else {
     fatal_error("Must specify either <upper_right> and <width> on a mesh.");
   }