Accidentally removed a line when I was merging the classes...

dune/solvers/solvers/quadraticipopt.hh

@@ -156,6 +156,9 @@ bool QuadraticIPOptProblem<MatrixType,VectorType>::
 get_nlp_info(Ipopt::Index& n, Ipopt::Index& m, Ipopt::Index& nnz_jac_g,
              Ipopt::Index& nnz_h_lag, Ipopt::TNLP::IndexStyleEnum& index_style)
 {
+    // use the C style indexing (0-based)
+    index_style = Ipopt::TNLP::C_STYLE;
+
     // Number of variables
     n = x_->dim();