diff --git a/examples/example_16/ob03235_2_full.yaml b/examples/example_16/ob03235_2_full.yaml
index dc1239b8..23780c8e 100644
--- a/examples/example_16/ob03235_2_full.yaml
+++ b/examples/example_16/ob03235_2_full.yaml
@@ -7,11 +7,12 @@ photometry_files:
 #    - {..., add_2450000: False}
 fit_method: EMCEE
 # Options: EMCEE, MultiNest, UltraNest.
-# If not given, EMCEE is used if starting_parameters are given; if prior_limits
-# are given, MultiNest or UltraNest is used depending on fitting_parameters.
-# If MultiNest/UltraNest is selected: starting_parameters, fit_constraints,
-# min_values and max_value cannot be provided. The trace plot cannot be
-# generated as well.
+# If fit_method is not given, EMCEE is used if starting_parameters are given;
+# and MultiNest or UltraNest is used if prior_limits are given, depending on
+# the combination of fitting_parameters.
+# If MultiNest/UltraNest is used, this file cannot have starting_parameters,
+# fit_constraints (except negative_blending_flux_sigma_mag and prior->t_E for
+# UltraNest), min_values, max_values and plots->trace.
 model:
     methods: 2452800. point_source 2452833. VBBL 2452845. point_source 2452860.
     default method: point_source_point_lens
@@ -108,7 +109,7 @@ fitting_parameters:
     ## UltraNest only (log directory, derived parameter names, show_status,
     ## dlogz=0.5, frac_remain=0.01, max_num_improvement_loops=-1)
     # log directory: ultranest_outputs/
-    # derived parameter names: flux_s_1 flux_b_1
+    # derived parameter names: flux_s_1 flux_b_1 flux_s_2 flux_b_2
     # show_status: True
     # dlogz: 2.
     # frac_remain: 0.5
diff --git a/examples/example_16/ulens_model_fit.py b/examples/example_16/ulens_model_fit.py
index 54b9e68f..5bdfe6d2 100644
--- a/examples/example_16/ulens_model_fit.py
+++ b/examples/example_16/ulens_model_fit.py
@@ -1372,11 +1372,9 @@ def _get_n_walkers(self):
         if 'n_walkers' in self._fitting_parameters:
             self._n_walkers = self._fitting_parameters['n_walkers']
         else:
-            if self._starting_parameters_type == 'file':
-                self._n_walkers = None
-            elif self._starting_parameters_type == 'draw':
+            if self._starting_parameters_type == 'draw':
                 self._n_walkers = 4 * self._n_fit_parameters
-            else:
+            elif self._starting_parameters_type != 'file':
                 raise ValueError(
                     'Unexpected: ' + self._starting_parameters_type)