diff --git a/docs/changelog.md b/docs/changelog.md
index 923c310..98493fe 100644
--- a/docs/changelog.md
+++ b/docs/changelog.md
@@ -2,6 +2,10 @@
 
 This project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html) and [Keep a Changelog](https://keepachangelog.com/en/1.0.0/) format.
 
+## [0.12.3] -- 2025-04-03
+- Fixed models for schema records and versions
+
+
 ## [0.12.2] -- 2025-03-27
 - Fixed links between schema and project
 
diff --git a/pepdbagent/_version.py b/pepdbagent/_version.py
index 76da4a9..8e1395b 100644
--- a/pepdbagent/_version.py
+++ b/pepdbagent/_version.py
@@ -1 +1 @@
-__version__ = "0.12.2"
+__version__ = "0.12.3"
diff --git a/pepdbagent/models.py b/pepdbagent/models.py
index b37b181..95aa783 100644
--- a/pepdbagent/models.py
+++ b/pepdbagent/models.py
@@ -264,8 +264,8 @@ class SchemaVersionAnnotation(BaseModel):
     namespace: str
     schema_name: str
     version: str
-    contributors: Optional[str] = ""
-    release_notes: Optional[str] = ""
+    contributors: Optional[Union[str, None]] = ""
+    release_notes: Optional[Union[str, None]] = ""
     tags: Dict[str, Union[str, None]] = {}
     release_date: datetime.datetime
     last_update_date: datetime.datetime
@@ -278,11 +278,11 @@ class SchemaRecordAnnotation(BaseModel):
 
     namespace: str
     schema_name: str
-    description: Optional[str] = ""
-    maintainers: str = ""
-    lifecycle_stage: str = ""
-    latest_released_version: str
-    private: bool = False
+    description: Optional[Union[str, None]] = ""
+    maintainers: Optional[Union[str, None]] = ""
+    lifecycle_stage: Optional[Union[str, None]] = ""
+    latest_released_version: Optional[Union[str, None]]
+    private: Optional[bool] = False
     last_update_date: datetime.datetime
 
 
@@ -305,17 +305,17 @@ class SchemaVersionSearchResult(BaseModel):
 
 
 class UpdateSchemaRecordFields(BaseModel):
-    maintainers: Optional[str] = None
-    lifecycle_stage: Optional[str] = None
+    maintainers: Optional[Union[str, None]] = None
+    lifecycle_stage: Optional[Union[str, None]] = None
     private: Optional[bool] = False
-    name: Optional[str] = None
-    description: Optional[str] = None
+    name: Optional[Union[str, None]] = None
+    description: Optional[Union[str, None]] = None
 
 
 class UpdateSchemaVersionFields(BaseModel):
-    contributors: Optional[str] = None
+    contributors: Optional[Union[str, None]] = None
     schema_value: Optional[dict] = None
-    release_notes: Optional[str] = None
+    release_notes: Optional[Union[str, None]] = None
 
 
 class TarNamespaceModel(BaseModel):