diff --git a/gentopia/memory/embeddings.py b/gentopia/memory/embeddings.py
index 3055b74..4136530 100644
--- a/gentopia/memory/embeddings.py
+++ b/gentopia/memory/embeddings.py
@@ -27,6 +27,8 @@
 )
 from gentopia.memory.utils import get_from_dict_or_env
 
+from enum import Enum
+
 logger = logging.getLogger(__name__)
 
 
@@ -156,6 +158,9 @@ async def _async_embed_with_retry(**kwargs: Any) -> Any:
 
     return await _async_embed_with_retry(**kwargs)
 
+class SpecialAllow:
+    class ValueField(str, Enum):
+        VALID_VALUE = "all"
 
 class OpenAIEmbeddings(BaseModel, Embeddings):
     """Wrapper around OpenAI embedding models."""
@@ -173,8 +178,8 @@ class OpenAIEmbeddings(BaseModel, Embeddings):
     embedding_ctx_length: int = 8191
     openai_api_key: Optional[str] = None
     openai_organization: Optional[str] = None
-    allowed_special: Union[Literal["all"], Set[str]] = set()
-    disallowed_special: Union[Literal["all"], Set[str], Sequence[str]] = "all"
+    allowed_special: Union[SpecialAllow.ValueField, Set[str]] = set()
+    disallowed_special: Union[SpecialAllow.ValueField, Set[str], Sequence[str]] = "all"
     chunk_size: int = 1000
     """Maximum number of texts to embed in each batch"""
     max_retries: int = 6