diff --git a/azure/functions/decorators/blob.py b/azure/functions/decorators/blob.py
index e3de6f7c..9ed4ce2f 100644
--- a/azure/functions/decorators/blob.py
+++ b/azure/functions/decorators/blob.py
@@ -20,7 +20,7 @@ def __init__(self,
         if isinstance(source, BlobSource):
             self.source = source.value
         else:
-            self.source = source
+            self.source = source  # type: ignore
         super().__init__(name=name, data_type=data_type)
 
     @staticmethod