diff --git a/crates/assistant/src/completion_provider/anthropic.rs b/crates/assistant/src/completion_provider/anthropic.rs
index 669e8cb808be95f18b8b70ccd6673260ede7c78a..87236501a94d306d5d82502bb8daba48f689961b 100644
--- a/crates/assistant/src/completion_provider/anthropic.rs
+++ b/crates/assistant/src/completion_provider/anthropic.rs
@@ -236,7 +236,7 @@ pub fn preprocess_anthropic_request(request: &mut LanguageModelRequest) {
     }
 
     if !system_message.is_empty() {
-        request.messages.insert(
+        new_messages.insert(
             0,
             LanguageModelRequestMessage {
                 role: Role::System,