diff --git a/modules/processing_helpers.py b/modules/processing_helpers.py
index 1135ceccc..1d81bbd56 100644
--- a/modules/processing_helpers.py
+++ b/modules/processing_helpers.py
@@ -584,9 +584,9 @@ def update_sampler(p, sd_model, second_pass=False):
         if sampler_selection == 'None':
             return
         sampler = sd_samplers.find_sampler(sampler_selection)
-        if sampler is None:
-            log.warning(f'Sampler: "{sampler_selection}" not found')
-            sampler = sd_samplers.all_samplers_map.get("UniPC")
+        resolved = sampler is not None
+        if not resolved:
+            log.warning(f'Sampler: name="{sampler_selection}" not found')
         sched_override_keys = [
             'schedulers_prediction_type', 'schedulers_beta_schedule', 'schedulers_timesteps',
             'schedulers_sigma', 'schedulers_use_thresholding', 'schedulers_use_loworder',
@@ -596,8 +596,8 @@ def update_sampler(p, sd_model, second_pass=False):
             'schedulers_timestep_spacing', 'schedulers_timesteps_range',
         ]
         scheduler_overrides = {k: getattr(p, k) for k in sched_override_keys if getattr(p, k, None) is not None}
-        sampler = sd_samplers.create_sampler(sampler.name, sd_model, scheduler_overrides=scheduler_overrides)
-        if sampler is None or sampler_selection == 'Default':
+        sampler = sd_samplers.create_sampler(sampler.name if resolved else sampler_selection, sd_model, scheduler_overrides=scheduler_overrides)
+        if sampler is None or not resolved or sampler_selection == 'Default':
             if second_pass:
                 p.hr_sampler = 'Default'
             else:
diff --git a/modules/sd_samplers.py b/modules/sd_samplers.py
index d38ab0acf..ef46719ba 100644
--- a/modules/sd_samplers.py
+++ b/modules/sd_samplers.py
@@ -15,7 +15,7 @@ loaded_config = None
 
 def find_sampler(name:str):
     if name is None or name == 'None':
-        return all_samplers_map.get("UniPC", None)
+        return all_samplers_map.get("Default", None)
     for sampler in all_samplers:
         if sampler.name.lower() == name.lower() or name in sampler.aliases:
             return sampler
@@ -107,6 +107,8 @@ def create_sampler(name, model, scheduler_overrides=None):
         config = find_sampler_config(name)
 
     if config is None or config.constructor is None:
+        if debug or not shared.opts.schedulers_fallback:
+            raise ValueError(f'Sampler: name="{name}" unknown')
         return restore_default(model, name)
 
     from modules import sd_samplers_diffusers
@@ -126,16 +128,16 @@ def create_sampler(name, model, scheduler_overrides=None):
         pass
     elif (model is not None) and (is_flow and not requires_flow):
         log.error(f'Sampler: "{sampler.name}" cls={sampler.sampler.__class__.__name__} pipe={model.__class__.__name__} type={pred_type} model requires sampler with discrete prediction')
-        if not debug:
-            return restore_default(model, name)
-        else:
+        if debug or not shared.opts.schedulers_fallback:
             raise ValueError(f'Sampler: name="{sampler.name}" cls={sampler.sampler.__class__.__name__} type={pred_type} model requires sampler with discrete prediction')
+        else:
+            return restore_default(model, name)
     elif (model is not None) and (not is_flow and requires_flow):
         log.error(f'Sampler: "{sampler.name}" cls={sampler.sampler.__class__.__name__} pipe={model.__class__.__name__} type={pred_type} model requires sampler with flow prediction')
-        if not debug:
-            return restore_default(model, name)
-        else:
+        if debug or not shared.opts.schedulers_fallback:
             raise ValueError(f'Sampler: name="{sampler.name}" cls={sampler.sampler.__class__.__name__} type={pred_type} model requires sampler with flow prediction')
+        else:
+            return restore_default(model, name)
 
     # assign sampler
     if model is not None:
diff --git a/modules/sd_samplers_diffusers.py b/modules/sd_samplers_diffusers.py
index a6e10f63a..e69e426a7 100644
--- a/modules/sd_samplers_diffusers.py
+++ b/modules/sd_samplers_diffusers.py
@@ -519,6 +519,8 @@ class DiffusionSampler:
             log.error(f'Sampler: "{name}" {e}')
             if debug:
                 errors.display(e, 'Samplers')
+            if debug or not shared.opts.schedulers_fallback:
+                raise
             self.sampler = None
             return