pydantic
diff --git a/‎pydantic/_internal/_fields.py
Lines changed: 3 additions & 0 deletions b/‎pydantic/_internal/_fields.py
Lines changed: 3 additions & 0 deletions
diff --git a/‎pydantic/fields.py
Lines changed: 6 additions & 2 deletions b/‎pydantic/fields.py
Lines changed: 6 additions & 2 deletions
diff --git a/‎tests/test_forward_ref.py
Lines changed: 24 additions & 1 deletion b/‎tests/test_forward_ref.py
Lines changed: 24 additions & 1 deletion
@@ -307,6 +307,9 @@ def rebuild_model_fields(
 
     This function should be called whenever a model with incomplete fields is encountered.
 
+    Raises:
+        NameError: If one of the annotations failed to evaluate.
+
     Note:
         This function *doesn't* mutate the model fields in place, as it can be called during
         schema generation, where you don't want to mutate other model's fields.
 
@@ -692,8 +692,12 @@ def apply_typevars_map(
             pydantic._internal._generics.replace_types is used for replacing the typevars with
                 their concrete types.
         """
-        annotation, _ = _typing_extra.try_eval_type(self.annotation, globalns, localns)
-        self.annotation = _generics.replace_types(annotation, typevars_map)
+        annotation = _generics.replace_types(self.annotation, typevars_map)
+        annotation, evaluated = _typing_extra.try_eval_type(annotation, globalns, localns)
+        self.annotation = annotation
+        if not evaluated:
+            self._complete = False
+            self._original_annotation = self.annotation
 
     def __repr_args__(self) -> ReprArgs:
         yield 'annotation', _repr.PlainRepr(_repr.display_as_type(self.annotation))
 
@@ -3,7 +3,7 @@
 import re
 import sys
 import typing
-from typing import Any, Optional
+from typing import Any, Generic, Optional, TypeVar
 
 import pytest
 
@@ -1232,6 +1232,29 @@ class SubChild(Child):
     )
 
 
+@pytest.mark.skipif(
+    sys.version_info < (3, 11),
+    reason=(
+        'Forward refs inside PEP 585 generics are not evaluated (see https://github.com/python/cpython/pull/30900).'
+    ),
 )
+def test_forward_ref_in_class_parameter() -> None:
+    """https://github.com/pydantic/pydantic/issues/11854"""
+    T = TypeVar('T')
+
+    class Model(BaseModel, Generic[T]):
+        f: T
+
+    M = Model[list['Undefined']]
+
+    assert not M.__pydantic_fields_complete__
+
+    M.model_rebuild(_types_namespace={'Undefined': int})
+
+    assert M.__pydantic_fields_complete__
+    assert M.model_fields['f'].annotation == list[int]
+
+
 def test_uses_the_local_namespace_when_generating_schema():
     def func():
         A = int