diff --git a/cli/tests/unit/text_encoding_test.ts b/cli/tests/unit/text_encoding_test.ts
index 58905157a943d6..c7c07f9373c2cf 100644
--- a/cli/tests/unit/text_encoding_test.ts
+++ b/cli/tests/unit/text_encoding_test.ts
@@ -69,7 +69,7 @@ unitTest(function btoaFailed(): void {
   const text = "你好";
   assertThrows(() => {
     btoa(text);
-  }, TypeError);
+  }, DOMException);
 });
 
 unitTest(function textDecoder2(): void {
diff --git a/op_crates/web/08_text_encoding.js b/op_crates/web/08_text_encoding.js
index c9d70874077e99..c3e622c994f237 100644
--- a/op_crates/web/08_text_encoding.js
+++ b/op_crates/web/08_text_encoding.js
@@ -26,6 +26,7 @@
 "use strict";
 
 ((window) => {
+  const webidl = window.__bootstrap.webidl;
   const core = Deno.core;
 
   const CONTINUE = null;
@@ -124,13 +125,17 @@
   }
 
   function btoa(s) {
+    s = webidl.converters.DOMString(s, {
+      prefix: "Failed to execute 'bota'",
+      context: "Argument 1",
+    });
     const byteArray = [];
     for (let i = 0; i < s.length; i++) {
       const charCode = s[i].charCodeAt(0);
       if (charCode > 0xff) {
-        throw new TypeError(
-          "The string to be encoded contains characters " +
-            "outside of the Latin1 range.",
+        throw new DOMException(
+          "The string to be encoded contains characters outside of the Latin1 range.",
+          "InvalidCharacterError",
         );
       }
       byteArray.push(charCode);
diff --git a/tools/wpt/expectation.json b/tools/wpt/expectation.json
index 00f0040486c89d..b2df7e407b9a23 100644
--- a/tools/wpt/expectation.json
+++ b/tools/wpt/expectation.json
@@ -1041,6 +1041,9 @@
   },
   "html": {
     "webappapis": {
+      "atob": {
+        "base64.any.js": true
+      },
       "timers": {
         "cleartimeout-clearinterval.any.js": true,
         "missing-timeout-setinterval.any.js": true,