diff --git a/moli-content-type/src/response.rs b/moli-content-type/src/response.rs
index c9a1269bfa..befe3bdddb 100644
--- a/moli-content-type/src/response.rs
+++ b/moli-content-type/src/response.rs
@@ -3,6 +3,7 @@
 pub struct ResponseContentType {
     mime_type: String,
     parameters: Vec<(String, String)>,
+    charset: Option<String>,
 }
 
 impl ResponseContentType {
@@ -24,9 +25,10 @@ impl ResponseContentType {
             .map(|(_, value)| value.as_str())
     }
 
-    /// The first `charset` value, with HTTP linear whitespace trimmed.
+    /// The first `charset` value, with HTTP linear whitespace trimmed and
+    /// ASCII letters lowercased to match Chromium's response metadata.
     pub fn charset(&self) -> Option<&str> {
-        self.parameter("charset").map(trim_http_lws)
+        self.charset.as_deref()
     }
 
     /// The first `boundary` value, with HTTP linear whitespace trimmed.
@@ -97,9 +99,15 @@ pub fn parse_response_content_type(input: &str) -> Option<ResponseContentType> {
         parameters.push((name, value));
     }
 
+    let charset = parameters
+        .iter()
+        .find(|(name, _)| name.eq_ignore_ascii_case("charset"))
+        .map(|(_, value)| trim_http_lws(value).to_ascii_lowercase());
+
     Some(ResponseContentType {
         mime_type,
         parameters,
+        charset,
     })
 }
 
diff --git a/moli-content-type/src/tests.rs b/moli-content-type/src/tests.rs
index fc9b5dd4d7..66d422df82 100644
--- a/moli-content-type/src/tests.rs
+++ b/moli-content-type/src/tests.rs
@@ -151,6 +151,14 @@ fn response_parser_http_lws_is_only_space_and_tab() {
     );
 }
 
+#[test]
+fn response_parser_ascii_lowercases_charset_without_changing_raw_parameters() {
+    let parsed = parse_response_content_type("text/html; charset=\tX-\u{dc}TF-A\t").unwrap();
+
+    assert_eq!(parsed.charset(), Some("x-\u{dc}tf-a"));
+    assert_eq!(parsed.parameter("charset"), Some("X-\u{dc}TF-A"));
+}
+
 #[test]
 fn response_parser_has_a_distinct_network_level_validity_boundary() {
     assert!(parse_response_content_type("garbage; charset=utf-8").is_none());
@@ -172,7 +180,7 @@ fn response_parser_matches_chromium_http_util_regression_matrix() {
     for (input, mime_type, charset) in [
         ("text/html", Some("text/html"), None),
         ("text/html;", Some("text/html"), None),
-        ("text/html; charset=utf-8", Some("text/html"), Some("utf-8")),
+        ("text/html; charset=UTF-8", Some("text/html"), Some("utf-8")),
         ("text/html; charset =utf-8", Some("text/html"), None),
         (
             "text/html; charset= utf-8",