diff --git a/aioboto3/s3/inject.py b/aioboto3/s3/inject.py
index <HASH>..<HASH> 100644
--- a/aioboto3/s3/inject.py
+++ b/aioboto3/s3/inject.py
@@ -77,6 +77,8 @@ async def download_fileobj(self, Bucket, Key, Fileobj, ExtraArgs=None,
     """
 
     try:
+        if ExtraArgs is None:
+            ExtraArgs = {}
         resp = await self.get_object(Bucket=Bucket, Key=Key, **ExtraArgs)
     except ClientError as err:
         if err.response['Error']['Code'] == 'NoSuchKey':
[noref] Default ExtraArgs to {} if None before expanding