diff --git a/server/davidia/server/fastapi_utils.py b/server/davidia/server/fastapi_utils.py
index 93a73ce..8ffde5f 100644
--- a/server/davidia/server/fastapi_utils.py
+++ b/server/davidia/server/fastapi_utils.py
@@ -148,14 +148,15 @@ async def root_request(payload: MyModel) -> OtherModel:
 
     def _instantiate_obj(model_class, obj):
         if isinstance(model_class, UnionType):
+            excs = {}
             for m in get_args(model_class):
                 try:
                     return m.model_validate(obj)
-                except ValidationError:
-                    logger.warning(
-                        "Could not validate as %s: %s", m, obj, exc_info=True
-                    )
+                except ValidationError as e:
+                    excs[m] = e
             logger.error("No valid models for", obj)
+            for m,e in excs.items():
+                logger.error("%s: %s", m, e)
             return None
 
         if isinstance(obj, BaseModel):
diff --git a/server/demos/simple.py b/server/demos/simple.py
index 73394a0..6853c38 100644
--- a/server/demos/simple.py
+++ b/server/demos/simple.py
@@ -1,3 +1,4 @@
+from davidia.models.selections import AnySelection
 from time import sleep
 
 import numpy as np
@@ -179,8 +180,7 @@ def table_demo(p):
 
 
 def regions_demo(p):
-    region(
-        selections=[
+    selections: list[AnySelection] = [
             RectangularSelection(
                 start=(3.5, 6.5),
                 lengths=(3.2, 2.0),
@@ -191,7 +191,9 @@ def regions_demo(p):
             LinearSelection(
                 start=(6.9, 10.5), length=2.0, angle=1.1, colour="cyan", alpha=0.6
             ),
-        ],
+        ]
+    region(
+        selections=selections,
         plot_id=f"plot_{p}",
     )
     rs = region(plot_id=f"plot_{p}")