diff --git a/src/ModelTree.hh b/src/ModelTree.hh
index de892f53a4f8a34c97ceeff698e120dbfbb2d069..9f01ad33d79103f9d9deefe41ffa96308eb6ad10 100644
--- a/src/ModelTree.hh
+++ b/src/ModelTree.hh
@@ -2242,7 +2242,7 @@ ModelTree::writeDriverSparseIndicesHelper(ostream &output) const
   output << "]);" << endl;
 
   // Write indices for the sparse higher-order derivatives
-  for (int i {2}; i < computed_derivs_order; i++)
+  for (int i {2}; i <= computed_derivs_order; i++)
     {
       output << "M_." << model_name << "_g" << i << "_sparse_indices = int32([";
       for (const auto &[vidx, d] : derivatives[i])
@@ -2292,7 +2292,7 @@ ModelTree::writeJsonSparseIndicesHelper(ostream &output) const
   output << ']' << endl;
 
   // Write indices for the sparse higher-order derivatives
-  for (int i {2}; i < computed_derivs_order; i++)
+  for (int i {2}; i <= computed_derivs_order; i++)
     {
       output << R"(, ")" << model_name << "_g" << i << R"(_sparse_indices": [)";
       for (bool printed_something {false};