diff --git a/lib/sharepoint/client.rb b/lib/sharepoint/client.rb
index 02469c6..5046fd4 100644
--- a/lib/sharepoint/client.rb
+++ b/lib/sharepoint/client.rb
@@ -515,7 +515,7 @@ def with_authentication_header(h)
     end
 
     def auth_header
-      {"Authentication" => bearer_auth }
+      {"Authorization" => bearer_auth }
     end
 
     def base_url