diff --git a/internal/ceres/solver_impl.cc b/internal/ceres/solver_impl.cc
index 8217484..43c0be6 100644
--- a/internal/ceres/solver_impl.cc
+++ b/internal/ceres/solver_impl.cc
@@ -1482,7 +1482,7 @@
   cholmod_sparse* block_jacobian_transpose =
       ss.CreateSparseMatrix(tsm_block_jacobian_transpose.get());
 
-  vector<int> ordering(program->NumResidualBlocks(), -1);
+  vector<int> ordering(program->NumParameterBlocks(), -1);
   ss.ApproximateMinimumDegreeOrdering(block_jacobian_transpose, &ordering[0]);
   ss.Free(block_jacobian_transpose);