diff --git a/examples/acados_matlab_octave/linear_mpc/main.m b/examples/acados_matlab_octave/linear_mpc/main.m
index 59ee327720..5fa3a8d28c 100644
--- a/examples/acados_matlab_octave/linear_mpc/main.m
+++ b/examples/acados_matlab_octave/linear_mpc/main.m
@@ -130,7 +130,8 @@
     ocp_solver.solve();
 
     % check the solver output
-    if ocp_solver.get('status') ~= 0
+    status = ocp_solver.get('status');
+    if status ~= 0
         warning(['acados ocp solver failed with status ',num2str(status)]);
     end
 
diff --git a/examples/acados_matlab_octave/mocp_transition_example/formulate_single_integrator_ocp.m b/examples/acados_matlab_octave/mocp_transition_example/formulate_single_integrator_ocp.m
index 5da5e1cd5c..ccc65fead9 100644
--- a/examples/acados_matlab_octave/mocp_transition_example/formulate_single_integrator_ocp.m
+++ b/examples/acados_matlab_octave/mocp_transition_example/formulate_single_integrator_ocp.m
@@ -48,7 +48,7 @@
     ocp.constraints.ubu = [u_max];
     ocp.constraints.idxbu = [0];
 
-    ocp.constraints.x0 = settings.X0;
+    ocp.constraints.x0 = settings.X0(1);
 end
 
 
diff --git a/interfaces/acados_matlab_octave/AcadosOcp.m b/interfaces/acados_matlab_octave/AcadosOcp.m
index 929545cec5..7d849a3d36 100644
--- a/interfaces/acados_matlab_octave/AcadosOcp.m
+++ b/interfaces/acados_matlab_octave/AcadosOcp.m
@@ -264,6 +264,9 @@ function make_consistent(self, is_mocp_phase)
                 if nbx_0 ~= length(constraints.ubx_0) || nbx_0 ~= length(constraints.idxbx_0)
                     error('inconsistent dimension nbx_0, regarding idxbx_0, lbx_0, ubx_0.');
                 end
+                if min(constraints.idxbx_0) < 0 || max(constraints.idxbx_0) > (dims.nx-1)
+                    error(['idxbx_0 should contain (zero-based) indices between 0 and ', num2str(dims.nx-1)])
+                end
             elseif ~isempty(constraints.idxbx_0) || ~isempty(constraints.lbx_0) || ~isempty(constraints.ubx_0)
                 error('setting bounds on x: need idxbx_0, lbx_0, ubx_0, at least one missing.');
             else
@@ -281,6 +284,9 @@ function make_consistent(self, is_mocp_phase)
                 if nbx ~= length(constraints.ubx) || nbx ~= length(constraints.idxbx)
                     error('inconsistent dimension nbx, regarding idxbx, lbx, ubx.');
                 end
+                if min(constraints.idxbx) < 0 || max(constraints.idxbx) > (dims.nx-1)
+                    error(['idxbx should contain (zero-based) indices between 0 and ', num2str(dims.nx-1)])
+                end
             elseif ~isempty(constraints.idxbx) || ~isempty(constraints.lbx) || ~isempty(constraints.ubx)
                 error('setting bounds on x: need idxbx, lbx, ubx, at least one missing.');
             else
@@ -293,6 +299,9 @@ function make_consistent(self, is_mocp_phase)
                 if nbu ~= length(constraints.ubu) || nbu ~= length(constraints.idxbu)
                     error('inconsistent dimension nbu, regarding idxbu, lbu, ubu.');
                 end
+                if min(constraints.idxbu) < 0 || max(constraints.idxbu) > (dims.nu-1)
+                    error(['idxbu should contain (zero-based) indices between 0 and ', num2str(dims.nu-1)])
+                end
             elseif ~isempty(constraints.idxbu) || ~isempty(constraints.lbu) || ~isempty(constraints.ubu)
                 error('setting bounds on u: need idxbu, lbu, ubu, at least one missing.');
             else
@@ -348,6 +357,9 @@ function make_consistent(self, is_mocp_phase)
                 if nbx_e ~= length(constraints.ubx_e) || nbx_e ~= length(constraints.idxbx_e)
                     error('inconsistent dimension nbx_e, regarding Jbx_e, lbx_e, ubx_e.');
                 end
+                if min(constraints.idxbx_e) < 0 || max(constraints.idxbx_e) > (dims.nx-1)
+                    error(['idxbx_e should contain (zero-based) indices between 0 and ', num2str(dims.nx-1)])
+                end
             elseif ~isempty(constraints.idxbx_e) || ~isempty(constraints.lbx_e) || ~isempty(constraints.ubx_e)
                 error('setting bounds on x: need Jbx_e, lbx_e, ubx_e, at least one missing.');
             else