diff --git a/fastapi/dependencies/utils.py b/fastapi/dependencies/utils.py
index b4f1938b4..2f0b806ec 100644
--- a/fastapi/dependencies/utils.py
+++ b/fastapi/dependencies/utils.py
@@ -733,11 +733,23 @@ async def solve_dependencies(
     )
 
 
-def _allows_none(field: ModelField) -> bool:
-    origin = get_origin(field.type_)
-    return (origin is Union or origin is types.UnionType) and type(None) in get_args(
-        field.type_
-    )
+if PYDANTIC_V2:
+    if sys.hexversion >= 0x30A00000:
+
+        def _allows_none(field: ModelField) -> bool:
+            origin = get_origin(field.type_)
+            return (origin is Union or origin is types.UnionType) and type(
+                None
+            ) in get_args(field.type_)
+    else:
+
+        def _allows_none(field: ModelField) -> bool:
+            origin = get_origin(field.type_)
+            return origin is Union and type(None) in get_args(field.type_)
+else:
+
+    def _allows_none(field: ModelField) -> bool:
+        return field.allow_none
 
 
 def _validate_value_with_model_field(
diff --git a/tests/test_none_passed_when_null_received.py b/tests/test_none_passed_when_null_received.py
index 4d1b3b0a8..51d3991f0 100644
--- a/tests/test_none_passed_when_null_received.py
+++ b/tests/test_none_passed_when_null_received.py
@@ -10,7 +10,7 @@ DEFAULT = 1234567890
 
 endpoints = []
 
-if sys.hexversion >= 0x31000000:
+if sys.hexversion >= 0x30A0000:
     from typing import Annotated
 
     @app.post("/api1")
@@ -22,7 +22,7 @@ if sys.hexversion >= 0x31000000:
     endpoints.append("/api1")
 
 
-if sys.hexversion >= 0x30900000:
+if sys.hexversion >= 0x3090000:
     from typing import Annotated
 
     @app.post("/api2")