diff --git a/litellm/litellm_core_utils/prompt_templates/factory.py b/litellm/litellm_core_utils/prompt_templates/factory.py
index 574d53c8313..52762dc597e 100644
--- a/litellm/litellm_core_utils/prompt_templates/factory.py
+++ b/litellm/litellm_core_utils/prompt_templates/factory.py
@@ -2438,7 +2438,7 @@ def anthropic_messages_pt(
                                     anthropic_content_element=_document_content_element,
                                     original_content_element=m,
                                 )
-                                user_content.append(cast(AnthropicMessagesDocumentParam, _document_content_element))
+                                user_content.append(cast(AnthropicMessagesDocumentParam, _document_content_element))  # cast-ok: same union narrowing as above
                                 continue
                             # Bedrock invoke models have format: invoke/...
                             # Vertex AI Anthropic also doesn't support URL sources for images