diff --git a/internal/ceres/dense_sparse_matrix.h b/internal/ceres/dense_sparse_matrix.h
index e7ad14d..1e4d499 100644
--- a/internal/ceres/dense_sparse_matrix.h
+++ b/internal/ceres/dense_sparse_matrix.h
@@ -57,6 +57,7 @@
 #endif
 
   DenseSparseMatrix(int num_rows, int num_cols);
+  DenseSparseMatrix(int num_rows, int num_cols, bool reserve_diagonal);
 
   virtual ~DenseSparseMatrix() {}