diff --git a/README.md b/README.md
index 7e65007..25ede59 100644
--- a/README.md
+++ b/README.md
@@ -240,7 +240,7 @@ response = client.messages(
       {"role": "user", "content": [
         {
           "type":"image","source":
-          {"type":"base64","media_type":"image/png", imgbase64 }
+          {"type":"base64","media_type":"image/png", "data": imgbase64 }
         },
         {"type":"text","text":"What is this"}
         ]