diff --git a/codex-rs/tui/src/mention_codec.rs b/codex-rs/tui/src/mention_codec.rs
index a1c486c8f7..a49fc876d2 100644
--- a/codex-rs/tui/src/mention_codec.rs
+++ b/codex-rs/tui/src/mention_codec.rs
@@ -203,7 +203,7 @@ fn starts_plaintext_mention(text_bytes: &[u8], index: usize) -> bool {
     index == 0
         || text_bytes
             .get(index.saturating_sub(1))
-            .is_none_or(|byte| byte.is_ascii_whitespace())
+            .is_none_or(u8::is_ascii_whitespace)
 }
 
 fn ends_plaintext_mention(text_bytes: &[u8], index: usize) -> bool {