diff --git a/packages/backend-rs/src/util/check_word_mute.rs b/packages/backend-rs/src/util/check_word_mute.rs
index 865dc18c5..38e4b7f3e 100644
--- a/packages/backend-rs/src/util/check_word_mute.rs
+++ b/packages/backend-rs/src/util/check_word_mute.rs
@@ -79,7 +79,7 @@ fn check_word_mute_impl(
             let text_lower = text.to_lowercase();
             muted_word_list
                 .iter()
-                .all(|muted_word| text_lower.contains(muted_word))
+                .all(|muted_word| text_lower.contains(&muted_word.to_lowercase()))
         })
     }) || muted_patterns.iter().any(|muted_pattern| {
         Regex::new(convert_regex(muted_pattern).as_str())