diff --git a/ext/fetch/20_headers.js b/ext/fetch/20_headers.js
index 67c5d0e652..c35c745b58 100644
--- a/ext/fetch/20_headers.js
+++ b/ext/fetch/20_headers.js
@@ -15,12 +15,11 @@
   const {
     HTTP_TAB_OR_SPACE_PREFIX_RE,
     HTTP_TAB_OR_SPACE_SUFFIX_RE,
-    HTTP_WHITESPACE_PREFIX_RE,
-    HTTP_WHITESPACE_SUFFIX_RE,
     HTTP_TOKEN_CODE_POINT_RE,
     byteLowerCase,
     collectSequenceOfCodepoints,
     collectHttpQuotedString,
+    httpTrim,
   } = window.__bootstrap.infra;
   const {
     ArrayIsArray,
@@ -59,17 +58,7 @@
    * @returns {string}
    */
   function normalizeHeaderValue(potentialValue) {
-    potentialValue = StringPrototypeReplaceAll(
-      potentialValue,
-      HTTP_WHITESPACE_PREFIX_RE,
-      "",
-    );
-    potentialValue = StringPrototypeReplaceAll(
-      potentialValue,
-      HTTP_WHITESPACE_SUFFIX_RE,
-      "",
-    );
-    return potentialValue;
+    return httpTrim(potentialValue);
   }
 
   /**
@@ -95,7 +84,7 @@
 
   // Regex matching illegal chars in a header value
   // deno-lint-ignore no-control-regex
-  const ILLEGAL_VALUE_CHARS = /[\x00\x0A\x0D]/;
+  const ILLEGAL_VALUE_CHARS = /[\x00\x0A\x0D]/g;
 
   /**
    * https://fetch.spec.whatwg.org/#concept-headers-append
diff --git a/ext/web/00_infra.js b/ext/web/00_infra.js
index 7c065bcd3a..7098c95773 100644
--- a/ext/web/00_infra.js
+++ b/ext/web/00_infra.js
@@ -19,6 +19,7 @@
     TypeError,
     ArrayPrototypeJoin,
     StringPrototypeCharAt,
+    StringPrototypeMatch,
     StringPrototypeSlice,
     String,
     StringPrototypeReplace,
@@ -75,6 +76,9 @@
     "g",
   );
   const HTTP_WHITESPACE_MATCHER = regexMatcher(HTTP_WHITESPACE);
+  const HTTP_BETWEEN_WHITESPACE = new RegExp(
+    `^[${HTTP_WHITESPACE_MATCHER}]*(.*?)[${HTTP_WHITESPACE_MATCHER}]*$`,
+  );
   const HTTP_WHITESPACE_PREFIX_RE = new RegExp(
     `^[${HTTP_WHITESPACE_MATCHER}]+`,
     "g",
@@ -237,6 +241,33 @@
     return core.opSync("op_base64_decode", data);
   }
 
+  /**
+   * @param {string} char
+   * @returns {boolean}
+   */
+  function isHttpWhitespace(char) {
+    switch (char) {
+      case "\u0009":
+      case "\u000A":
+      case "\u000D":
+      case "\u0020":
+        return true;
+      default:
+        return false;
+    }
+  }
+
+  /**
+   * @param {string} s
+   * @returns {string}
+   */
+  function httpTrim(s) {
+    if (!isHttpWhitespace(s[0]) && !isHttpWhitespace(s[s.length - 1])) {
+      return s;
+    }
+    return StringPrototypeMatch(s, HTTP_BETWEEN_WHITESPACE)?.[1] ?? "";
+  }
+
   window.__bootstrap.infra = {
     collectSequenceOfCodepoints,
     ASCII_DIGIT,
@@ -254,6 +285,7 @@
     HTTP_TAB_OR_SPACE_SUFFIX_RE,
     HTTP_WHITESPACE_PREFIX_RE,
     HTTP_WHITESPACE_SUFFIX_RE,
+    httpTrim,
     regexMatcher,
     byteUpperCase,
     byteLowerCase,
diff --git a/ext/web/internal.d.ts b/ext/web/internal.d.ts
index 94fc9c1968..89fdbacf3c 100644
--- a/ext/web/internal.d.ts
+++ b/ext/web/internal.d.ts
@@ -29,6 +29,7 @@ declare namespace globalThis {
       HTTP_TAB_OR_SPACE_SUFFIX_RE: RegExp;
       HTTP_WHITESPACE_PREFIX_RE: RegExp;
       HTTP_WHITESPACE_SUFFIX_RE: RegExp;
+      httpTrim(s: string): string;
       regexMatcher(chars: string[]): string;
       byteUpperCase(s: string): string;
       byteLowerCase(s: string): string;