diff --git a/src/anthropic/_models.py b/src/anthropic/_models.py
index 5d95bb4b..eb7ce3bd 100644
--- a/src/anthropic/_models.py
+++ b/src/anthropic/_models.py
@@ -643,6 +643,14 @@ def validate_type(*, type_: type[_T], value: object) -> _T:
     return cast(_T, _validate_non_model_type(type_=type_, value=value))
 
 
+def set_pydantic_config(typ: Any, config: pydantic.ConfigDict) -> None:
+    """Add a pydantic config for the given type.
+
+    Note: this is a no-op on Pydantic v1.
+    """
+    setattr(typ, "__pydantic_config__", config)  # noqa: B010
+
+
 # our use of subclasssing here causes weirdness for type checkers,
 # so we just pretend that we don't subclass
 if TYPE_CHECKING:
diff --git a/src/anthropic/types/image_block_param.py b/src/anthropic/types/image_block_param.py
index 45236832..d7f46fa9 100644
--- a/src/anthropic/types/image_block_param.py
+++ b/src/anthropic/types/image_block_param.py
@@ -7,6 +7,7 @@
 
 from .._types import Base64FileInput
 from .._utils import PropertyInfo
+from .._models import set_pydantic_config
 
 __all__ = ["ImageBlockParam", "Source"]
 
@@ -19,6 +20,9 @@ class Source(TypedDict, total=False):
     type: Required[Literal["base64"]]
 
 
+set_pydantic_config(Source, {"arbitrary_types_allowed": True})
+
+
 class ImageBlockParam(TypedDict, total=False):
     source: Required[Source]