diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_webRequest_responseBody.js b/toolkit/components/extensions/test/xpcshell/test_ext_webRequest_responseBody.js
index 70f17052af93..629228caeb06 100644
--- a/toolkit/components/extensions/test/xpcshell/test_ext_webRequest_responseBody.js
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_webRequest_responseBody.js
@@ -81,40 +81,6 @@ server.registerPathHandler("/lorem.html.gz", async (request, response) => {
   response.finish();
 });
 
-server.registerPathHandler("/multipart", async (request, response) => {
-  response.processAsync();
-
-  response.setHeader(
-    "Content-Type",
-    'Content-Type: multipart/x-mixed-replace; boundary="testingtesting"',
-    false
-  );
-
-  response.write("--testingtesting\n");
-  response.write(PARTS.join(""));
-  response.write("--testingtesting--\n");
-
-  response.finish();
-});
-
-server.registerPathHandler("/multipart2", async (request, response) => {
-  response.processAsync();
-
-  response.setHeader(
-    "Content-Type",
-    'Content-Type: multipart/x-mixed-replace; boundary="testingtesting"',
-    false
-  );
-
-  response.write("--testingtesting\n");
-  response.write(PARTS.join(""));
-  response.write("--testingtesting\n");
-  response.write(PARTS.join(""));
-  response.write("--testingtesting--\n");
-
-  response.finish();
-});
-
 server.registerDirectory("/data/", do_get_file("data"));
 
 const TASKS = [
@@ -467,98 +433,6 @@ const TASKS = [
       equal(response, PARTS.join(""), "Got expected final HTML");
     },
   },
-  {
-    url: "multipart",
-    task(filter, resolve, num) {
-      let response = "";
-      let decoder = new TextDecoder("utf-8");
-
-      filter.onstart = event => {
-        browser.test.log(`(${num}): Request start`);
-      };
-
-      filter.onstop = event => {
-        filter.disconnect();
-        browser.test.assertEq(
-          "--testingtesting\n" + PARTS.join("") + "--testingtesting--\n",
-          JSON.stringify(response),
-          `(${num}): Got expected response`
-        );
-
-        resolve();
-      };
-
-      filter.ondata = event => {
-        let str = decoder.decode(event.data, { stream: true });
-        response += str;
-
-        filter.write(event.data);
-      };
-
-      filter.onerror = event => {
-        browser.test.fail(
-          `(${num}): Got unexpected error event: ${filter.error}`
-        );
-      };
-    },
-    verify(response) {
-      equal(
-        response,
-        "--testingtesting\n" + PARTS.join("") + "--testingtesting--\n",
-        "Got expected final HTML"
-      );
-    },
-  },
-  {
-    url: "multipart2",
-    task(filter, resolve, num) {
-      let response = "";
-      let decoder = new TextDecoder("utf-8");
-
-      filter.onstart = event => {
-        browser.test.log(`(${num}): Request start`);
-      };
-
-      filter.onstop = event => {
-        filter.disconnect();
-        browser.test.assertEq(
-          "--testingtesting\n" +
-            PARTS.join("") +
-            "--testingtesting\n" +
-            PARTS.join("") +
-            "--testingtesting--\n",
-          JSON.stringify(response),
-          `(${num}): Got expected response`
-        );
-
-        resolve();
-      };
-
-      filter.ondata = event => {
-        let str = decoder.decode(event.data, { stream: true });
-        response += str;
-
-        filter.write(event.data);
-      };
-
-      filter.onerror = event => {
-        browser.test.fail(
-          `(${num}): Got unexpected error event: ${filter.error}`
-        );
-      };
-    },
-    verify(response) {
-      equal(
-        response,
-        "--testingtesting\n" +
-          PARTS.join("") +
-          "--testingtesting\n" +
-          PARTS.join("") +
-          "--testingtesting--\n",
-        "Got expected final HTML"
-      );
-    },
-  },
 ];
 
 function serializeTest(test, num) {