diff --git a/pydantic_pystac_extensions/__init__.py b/pydantic_pystac_extensions/__init__.py
index 1baf9c758812945663873c618e5895d2b568b783..5340110429f0c703f77c278413aa5a9f29986a08 100644
--- a/pydantic_pystac_extensions/__init__.py
+++ b/pydantic_pystac_extensions/__init__.py
@@ -2,4 +2,4 @@
 
 from .core import create_extension_cls, BaseExtensionModel  # noqa
 
-__version__ = "0.1.4"
+__version__ = "0.1.5"
diff --git a/pydantic_pystac_extensions/core.py b/pydantic_pystac_extensions/core.py
index 928fb90f6c11363eec9020914853acb52c4afbad..9f281b178715684043c09b9b697173527502b1fb 100644
--- a/pydantic_pystac_extensions/core.py
+++ b/pydantic_pystac_extensions/core.py
@@ -13,7 +13,7 @@ from .schema import generate_schema
 class BaseExtensionModel(BaseModel):
     """Base class for extensions models."""
 
-    model_config = ConfigDict(populate_by_name=True)
+    model_config = ConfigDict(extra="forbid", populate_by_name=True)
 
 
 def create_extension_cls(model_cls: BaseModel, schema_uri: str) -> PropertiesExtension: