diff --git a/package-lock.json b/package-lock.json
index 8e498ba18..600c9082a 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -29,7 +29,7 @@
         "@types/sinonjs__fake-timers": "^8.1.5",
         "@vitest/coverage-v8": "^2.1.1",
         "esbuild": "^0.24.0",
-        "fetch-mock": "^11.0.0",
+        "fetch-mock": "^12.0.0",
         "glob": "^11.0.0",
         "prettier": "3.3.3",
         "proxy": "^2.0.0",
@@ -3006,25 +3006,20 @@
       }
     },
     "node_modules/fetch-mock": {
-      "version": "11.1.3",
-      "resolved": "https://registry.npmjs.org/fetch-mock/-/fetch-mock-11.1.3.tgz",
-      "integrity": "sha512-ATh0dWgnVrUHiiXuvQm1Ry+ThWfSv1QQgqJTCtybrNxyUrFiSOaDKsNG29eyysp1SHeNP6Q+dH50+8VifN51Ig==",
+      "version": "12.0.2",
+      "resolved": "https://registry.npmjs.org/fetch-mock/-/fetch-mock-12.0.2.tgz",
+      "integrity": "sha512-9KVq/Scz06A+ThORLA/J/EACiPzLdSn6DeLV61hni57kd3DXhQVCtkpj4LgwES+8osEVEfcqA6LwdSX2FYVK7w==",
       "dev": true,
       "license": "MIT",
       "dependencies": {
         "@types/glob-to-regexp": "^0.4.4",
         "dequal": "^2.0.3",
         "glob-to-regexp": "^0.4.1",
-        "is-subset": "^0.1.1",
+        "is-subset-of": "^3.1.10",
         "regexparam": "^3.0.0"
       },
       "engines": {
-        "node": ">=8.0.0"
-      },
-      "peerDependenciesMeta": {
-        "node-fetch": {
-          "optional": true
-        }
+        "node": ">=18.11.0"
       }
     },
     "node_modules/fflate": {
@@ -3640,11 +3635,16 @@
         "url": "https://github.com/sponsors/sindresorhus"
       }
     },
-    "node_modules/is-subset": {
-      "version": "0.1.1",
-      "resolved": "https://registry.npmjs.org/is-subset/-/is-subset-0.1.1.tgz",
-      "integrity": "sha512-6Ybun0IkarhmEqxXCNw/C0bna6Zb/TkfUX9UbwJtK6ObwAVCxmAP308WWTHviM/zAqXk05cdhYsUsZeGQh99iw==",
-      "dev": true
+    "node_modules/is-subset-of": {
+      "version": "3.1.10",
+      "resolved": "https://registry.npmjs.org/is-subset-of/-/is-subset-of-3.1.10.tgz",
+      "integrity": "sha512-avvaYgVmYWyaZ1NDFiv4y9JGkrE2je3op1Po4VYKKJKR8H2qVPsg1GZuuXl5elCTxTlwAIsrAjWAs4BVrISFRw==",
+      "deprecated": "Package no longer supported. Contact Support at https://www.npmjs.com/support for more info.",
+      "dev": true,
+      "license": "MIT",
+      "dependencies": {
+        "typedescriptor": "3.0.2"
+      }
     },
     "node_modules/is-unicode-supported": {
       "version": "2.0.0",
@@ -8857,6 +8857,14 @@
         "node": ">=4"
       }
     },
+    "node_modules/typedescriptor": {
+      "version": "3.0.2",
+      "resolved": "https://registry.npmjs.org/typedescriptor/-/typedescriptor-3.0.2.tgz",
+      "integrity": "sha512-hyVbaCUd18UiXk656g/imaBLMogpdijIEpnhWYrSda9rhvO4gOU16n2nh7xG5lv/rjumnZzGOdz0CEGTmFe0fQ==",
+      "deprecated": "Package no longer supported. Contact Support at https://www.npmjs.com/support for more info.",
+      "dev": true,
+      "license": "MIT"
+    },
     "node_modules/typescript": {
       "version": "5.1.3",
       "resolved": "https://registry.npmjs.org/typescript/-/typescript-5.1.3.tgz",
diff --git a/package.json b/package.json
index fc0a3ab6a..2a0530cfc 100644
--- a/package.json
+++ b/package.json
@@ -46,7 +46,7 @@
     "@types/sinonjs__fake-timers": "^8.1.5",
     "@vitest/coverage-v8": "^2.1.1",
     "esbuild": "^0.24.0",
-    "fetch-mock": "^11.0.0",
+    "fetch-mock": "^12.0.0",
     "glob": "^11.0.0",
     "prettier": "3.3.3",
     "proxy": "^2.0.0",
diff --git a/test/auth.test.ts b/test/auth.test.ts
index 651049947..1529d2f87 100644
--- a/test/auth.test.ts
+++ b/test/auth.test.ts
@@ -65,7 +65,7 @@ beforeEach(() => {
 
 describe("Authentication", () => {
   it("new Octokit({ auth: 'secret123' })", () => {
-    const mock = fetchMock.sandbox().getOnce(
+    const mock = fetchMock.createInstance().getOnce(
       "https://api.github.com/",
       { ok: true },
       {
@@ -80,7 +80,7 @@ describe("Authentication", () => {
     const octokit = new Octokit({
       auth: "secret123",
       request: {
-        fetch: mock,
+        fetch: mock.fetchHandler,
       },
     });
 
@@ -88,7 +88,7 @@ describe("Authentication", () => {
   });
 
   it("new Octokit({ auth: 'token secret123' })", () => {
-    const mock = fetchMock.sandbox().getOnce(
+    const mock = fetchMock.createInstance().getOnce(
       "https://api.github.com/",
       { ok: true },
       {
@@ -103,7 +103,7 @@ describe("Authentication", () => {
     const octokit = new Octokit({
       auth: "token secret123",
       request: {
-        fetch: mock,
+        fetch: mock.fetchHandler,
       },
     });
 
@@ -111,7 +111,7 @@ describe("Authentication", () => {
   });
 
   it("new Octokit({ auth: 'Token secret123' })", () => {
-    const mock = fetchMock.sandbox().getOnce(
+    const mock = fetchMock.createInstance().getOnce(
       "https://api.github.com/",
       { ok: true },
       {
@@ -126,7 +126,7 @@ describe("Authentication", () => {
     const octokit = new Octokit({
       auth: "Token secret123",
       request: {
-        fetch: mock,
+        fetch: mock.fetchHandler,
       },
     });
 
@@ -136,7 +136,7 @@ describe("Authentication", () => {
   const BEARER_TOKEN =
     "eyJhbGciOiJSUzI1NiIsInR5cCI6IkpXVCJ9.eyJpYXQiOjE1NTM4MTkzMTIsImV4cCI6MTU1MzgxOTM3MiwiaXNzIjoxfQ.etiSZ4LFQZ8tiMGJVqKDoGn8hxMCgwL4iLvU5xBUqbAPr4pbk_jJZmMQjuxTlOnRxq4e7NouTizGCdfohRMb3R1mpLzGPzOH9_jqSA_BWYxolsRP_WDSjuNcw6nSxrPRueMVRBKFHrqcTOZJej0djRB5pI61hDZJ_-DGtiOIFexlK3iuVKaqBkvJS5-TbTekGuipJ652g06gXuz-l8i0nHiFJldcuIruwn28hTUrjgtPbjHdSBVn_QQLKc2Fhij8OrhcGqp_D_fvb_KovVmf1X6yWiwXV5VXqWARS-JGD9JTAr2495ZlLV_E4WPxdDpz1jl6XS9HUhMuwBpaCOuipw";
   it("new Octokit({ auth: BEARER_TOKEN })", () => {
-    const mock = fetchMock.sandbox().getOnce(
+    const mock = fetchMock.createInstance().getOnce(
       "https://api.github.com/",
       { ok: true },
       {
@@ -151,7 +151,7 @@ describe("Authentication", () => {
     const octokit = new Octokit({
       auth: BEARER_TOKEN,
       request: {
-        fetch: mock,
+        fetch: mock.fetchHandler,
       },
     });
 
@@ -163,7 +163,7 @@ describe("Authentication", () => {
     const CLIENT_SECRET = "0123secret";
     const CODE = "code123";
 
-    const mock = fetchMock.sandbox().postOnce(
+    const mock = fetchMock.createInstance().postOnce(
       "https://github.com/login/oauth/access_token",
       {
         access_token: "token123",
@@ -182,7 +182,7 @@ describe("Authentication", () => {
     const MyOctokit = Octokit.defaults({
       authStrategy: createOAuthAppAuth,
       request: {
-        fetch: mock,
+        fetch: mock.fetchHandler,
       },
     });
 
@@ -198,12 +198,12 @@ describe("Authentication", () => {
       code: CODE,
     });
 
-    expect(mock.done()).toBe(true);
+    expect(mock.callHistory.done()).toBe(true);
   });
 
   it("auth = createAppAuth()", async () => {
     const mock = fetchMock
-      .sandbox()
+      .createInstance()
       .postOnce("https://api.github.com/app/installations/123/access_tokens", {
         token: "secret123",
         expires_at: "1970-01-01T01:00:00.000Z",
@@ -242,7 +242,7 @@ describe("Authentication", () => {
         installationId: 123,
       },
       request: {
-        fetch: mock,
+        fetch: mock.fetchHandler,
       },
     });
 
@@ -251,11 +251,11 @@ describe("Authentication", () => {
 
     await octokit.request("GET /app");
 
-    expect(mock.done()).toBe(true);
+    expect(mock.callHistory.done()).toBe(true);
   });
 
   it("auth = createActionAuth()", async () => {
-    const mock = fetchMock.sandbox().getOnce(
+    const mock = fetchMock.createInstance().getOnce(
       "https://api.github.com/app",
       { id: 123 },
       {
@@ -275,7 +275,7 @@ describe("Authentication", () => {
     const octokit = new Octokit({
       authStrategy: createActionAuth,
       request: {
-        fetch: mock,
+        fetch: mock.fetchHandler,
       },
     });
 
@@ -303,7 +303,7 @@ describe("Authentication", () => {
 
   it("createAppAuth with GraphQL + GHES (probot/probot#1386)", async () => {
     const mock = fetchMock
-      .sandbox()
+      .createInstance()
       .postOnce(
         "https://fake.github-enterprise.com/api/v3/app/installations/123/access_tokens",
         {
@@ -334,7 +334,7 @@ describe("Authentication", () => {
       },
       baseUrl: "https://fake.github-enterprise.com/api/v3",
       request: {
-        fetch: mock,
+        fetch: mock.fetchHandler,
       },
     });
 
@@ -344,12 +344,12 @@ describe("Authentication", () => {
       }
     }`);
 
-    expect(mock.done()).toBe(true);
+    expect(mock.callHistory.done()).toBe(true);
   });
 
   it("should pass through the logger (#1277)", async () => {
     const mock = fetchMock
-      .sandbox()
+      .createInstance()
       .postOnce("https://api.github.com/app/installations/2/access_tokens", {
         token: "installation-token-123",
         permissions: {},
@@ -377,7 +377,7 @@ describe("Authentication", () => {
         installationId: 2,
       },
       request: {
-        fetch: mock,
+        fetch: mock.fetchHandler,
       },
     });
 
diff --git a/test/constructor.test.ts b/test/constructor.test.ts
index aecce2d31..55a4d5d23 100644
--- a/test/constructor.test.ts
+++ b/test/constructor.test.ts
@@ -4,7 +4,7 @@ import { describe, expect, it } from "vitest";
 
 describe("Smoke test", () => {
   it("previews option", () => {
-    const mock = fetchMock.sandbox().getOnce(
+    const mock = fetchMock.createInstance().getOnce(
       "https://api.github.com/graphql",
       { ok: true },
       {
@@ -22,7 +22,7 @@ describe("Smoke test", () => {
         "symmetra",
       ],
       request: {
-        fetch: mock,
+        fetch: mock.fetchHandler,
       },
     });
 
@@ -30,7 +30,7 @@ describe("Smoke test", () => {
   });
 
   it("timeZone option", () => {
-    const mock = fetchMock.sandbox().getOnce(
+    const mock = fetchMock.createInstance().getOnce(
       "https://api.github.com/",
       { ok: true },
       {
@@ -44,7 +44,7 @@ describe("Smoke test", () => {
     const octokit = new Octokit({
       timeZone: "Europe/Amsterdam",
       request: {
-        fetch: mock,
+        fetch: mock.fetchHandler,
       },
     });
 
diff --git a/test/defaults.test.ts b/test/defaults.test.ts
index 69fe4f2be..e7502650c 100644
--- a/test/defaults.test.ts
+++ b/test/defaults.test.ts
@@ -13,7 +13,7 @@ describe("Octokit.defaults", () => {
   });
 
   it("Octokit.defaults({baseUrl})", () => {
-    const mock = fetchMock.sandbox().getOnce(
+    const mock = fetchMock.createInstance().getOnce(
       "https://github.acme-inc.test/api/v3/",
       { ok: true },
       {
@@ -27,7 +27,7 @@ describe("Octokit.defaults", () => {
     const OctokitWithDefaults = Octokit.defaults({
       baseUrl: "https://github.acme-inc.test/api/v3",
       request: {
-        fetch: mock,
+        fetch: mock.fetchHandler,
       },
     });
 
@@ -37,7 +37,7 @@ describe("Octokit.defaults", () => {
   });
 
   it("Octokit.defaults({userAgent})", () => {
-    const mock = fetchMock.sandbox().getOnce(
+    const mock = fetchMock.createInstance().getOnce(
       "https://api.github.com/",
       { ok: true },
       {
@@ -51,7 +51,7 @@ describe("Octokit.defaults", () => {
     const OctokitWithDefaults = Octokit.defaults({
       userAgent: "my-app/1.2.3",
       request: {
-        fetch: mock,
+        fetch: mock.fetchHandler,
       },
     });
 
@@ -61,7 +61,7 @@ describe("Octokit.defaults", () => {
   });
 
   it("Octokit.defaults({userAgent}) with userAgent Constructor Option", () => {
-    const mock = fetchMock.sandbox().getOnce(
+    const mock = fetchMock.createInstance().getOnce(
       "https://api.github.com/",
       { ok: true },
       {
@@ -75,7 +75,7 @@ describe("Octokit.defaults", () => {
     const OctokitWithDefaults = Octokit.defaults({
       userAgent: "my-octokit.js/1.2.3",
       request: {
-        fetch: mock,
+        fetch: mock.fetchHandler,
       },
     });
 
@@ -87,7 +87,7 @@ describe("Octokit.defaults", () => {
   });
 
   it("Octokit.defaults({timeZone})", () => {
-    const mock = fetchMock.sandbox().getOnce(
+    const mock = fetchMock.createInstance().getOnce(
       "https://api.github.com/",
       { ok: true },
       {
@@ -102,7 +102,7 @@ describe("Octokit.defaults", () => {
     const OctokitWithDefaults = Octokit.defaults({
       timeZone: "Europe/Amsterdam",
       request: {
-        fetch: mock,
+        fetch: mock.fetchHandler,
       },
     });
 
@@ -112,7 +112,7 @@ describe("Octokit.defaults", () => {
   });
 
   it("Octokit.defaults({ auth })", async () => {
-    const mock = fetchMock.sandbox().getOnce(
+    const mock = fetchMock.createInstance().getOnce(
       "https://api.github.com/app",
       { id: 123 },
       {
@@ -132,7 +132,7 @@ describe("Octokit.defaults", () => {
     const OctokitWithDefaults = Octokit.defaults({
       authStrategy: createActionAuth,
       request: {
-        fetch: mock,
+        fetch: mock.fetchHandler,
       },
     });
 
@@ -143,7 +143,7 @@ describe("Octokit.defaults", () => {
   });
 
   it("Octokit.defaults().defaults()", () => {
-    const mock = fetchMock.sandbox().getOnce(
+    const mock = fetchMock.createInstance().getOnce(
       "https://github.acme-inc.test/api/v3/",
       { ok: true },
       {
@@ -157,7 +157,7 @@ describe("Octokit.defaults", () => {
     const OctokitWithDefaults = Octokit.defaults({
       baseUrl: "https://github.acme-inc.test/api/v3",
       request: {
-        fetch: mock,
+        fetch: mock.fetchHandler,
       },
     }).defaults({
       userAgent: "my-app/1.2.3",
@@ -169,7 +169,7 @@ describe("Octokit.defaults", () => {
   });
 
   it("Octokit.plugin().defaults()", () => {
-    const mock = fetchMock.sandbox().getOnce(
+    const mock = fetchMock.createInstance().getOnce(
       "https://github.acme-inc.test/api/v3/",
       { ok: true },
       {
@@ -187,7 +187,7 @@ describe("Octokit.defaults", () => {
     }).defaults({
       baseUrl: "https://github.acme-inc.test/api/v3",
       request: {
-        fetch: mock,
+        fetch: mock.fetchHandler,
       },
     });
 
diff --git a/test/graphql.test.ts b/test/graphql.test.ts
index 7679cc6e8..f1f6fad94 100644
--- a/test/graphql.test.ts
+++ b/test/graphql.test.ts
@@ -18,9 +18,11 @@ describe("octokit.graphql()", () => {
       },
     };
     const mock = fetchMock
-      .sandbox()
+      .createInstance()
       .postOnce("https://api.github.com/graphql", (_url, request) => {
-        const body = JSON.parse(request.body!.toString());
+        const body = JSON.parse(
+          mock.callHistory.calls()[0].options.body!.toString(),
+        );
         expect(body.query).toEqual(query);
 
         return {
@@ -31,7 +33,7 @@ describe("octokit.graphql()", () => {
     const octokit = new Octokit({
       auth: `secret123`,
       request: {
-        fetch: mock,
+        fetch: mock.fetchHandler,
       },
     });
 
@@ -57,9 +59,11 @@ describe("octokit.graphql()", () => {
       },
     };
     const mock = fetchMock
-      .sandbox()
+      .createInstance()
       .postOnce("https://github.acme-inc.com/api/graphql", (_url, request) => {
-        const body = JSON.parse(request.body!.toString());
+        const body = JSON.parse(
+          mock.callHistory.calls()[0].options.body!.toString(),
+        );
         expect(body.query).toEqual(query);
 
         return {
@@ -71,7 +75,7 @@ describe("octokit.graphql()", () => {
       auth: `secret123`,
       baseUrl: "https://github.acme-inc.com/api/v3",
       request: {
-        fetch: mock,
+        fetch: mock.fetchHandler,
       },
     });
 
@@ -90,10 +94,13 @@ describe("octokit.graphql()", () => {
 
   it("custom headers: octokit.graphql({ query, headers })", async () => {
     const mock = fetchMock
-      .sandbox()
+      .createInstance()
       .postOnce("https://api.github.com/graphql", (_url, request) => {
         // @ts-ignore `request.headers` are typed incorrectly by fetch-mock
-        expect(request.headers["x-custom"]).toEqual("value");
+
+        expect(mock.callHistory.calls()[0].options.headers["x-custom"]).toEqual(
+          "value",
+        );
 
         return {
           data: { ok: true },
@@ -103,7 +110,7 @@ describe("octokit.graphql()", () => {
     const octokit = new Octokit({
       auth: `secret123`,
       request: {
-        fetch: mock,
+        fetch: mock.fetchHandler,
       },
     });
 
@@ -119,12 +126,16 @@ describe("octokit.graphql()", () => {
 
   it("custom headers: octokit.graphql(query, { headers })", async () => {
     const mock = fetchMock
-      .sandbox()
+      .createInstance()
       .postOnce("https://api.github.com/graphql", (_url, request) => {
         // @ts-ignore `request.headers` are typed incorrectly by fetch-mock
-        expect(request.headers["x-custom"]).toEqual("value");
+        expect(mock.callHistory.calls()[0].options.headers["x-custom"]).toEqual(
+          "value",
+        );
 
-        const body = JSON.parse(request.body!.toString());
+        const body = JSON.parse(
+          mock.callHistory.calls()[0].options.body!.toString(),
+        );
         expect(body.variables).toEqual({ foo: "bar" });
 
         return {
@@ -135,7 +146,7 @@ describe("octokit.graphql()", () => {
     const octokit = new Octokit({
       auth: `secret123`,
       request: {
-        fetch: mock,
+        fetch: mock.fetchHandler,
       },
     });
 
diff --git a/test/hook.test.ts b/test/hook.test.ts
index d073fba95..c29c7a86a 100644
--- a/test/hook.test.ts
+++ b/test/hook.test.ts
@@ -30,7 +30,7 @@ describe("octokit.hook", () => {
 
   it("octokit.hook.before('request')", () => {
     const mock = fetchMock
-      .sandbox()
+      .createInstance()
       .getOnce(
         "https://api.github.com/foo/daz/baz?qux=quux&beforeAddition=works",
         { ok: true },
@@ -38,7 +38,7 @@ describe("octokit.hook", () => {
 
     const octokit = new Octokit({
       request: {
-        fetch: mock,
+        fetch: mock.fetchHandler,
       },
     });
 
@@ -61,7 +61,7 @@ describe("octokit.hook", () => {
         bar: "daz",
         qux: "quux",
         request: {
-          fetch: mock,
+          fetch: mock.fetchHandler,
           // @ts-ignore
           hook: options.request.hook,
         },
@@ -86,12 +86,12 @@ describe("octokit.hook", () => {
 
   it("octokit.hook.after('request')", async () => {
     const mock = fetchMock
-      .sandbox()
+      .createInstance()
       .getOnce("https://api.github.com/", { ok: true });
 
     const octokit = new Octokit({
       request: {
-        fetch: mock,
+        fetch: mock.fetchHandler,
       },
     });
 
@@ -109,7 +109,7 @@ describe("octokit.hook", () => {
           format: "",
         },
         request: {
-          fetch: mock,
+          fetch: mock.fetchHandler,
           hook: requestOptions.request.hook,
         },
       });
@@ -126,11 +126,13 @@ describe("octokit.hook", () => {
   });
 
   it("octokit.hook.error('request')", async () => {
-    const mock = fetchMock.sandbox().getOnce("https://api.github.com/", 500);
+    const mock = fetchMock
+      .createInstance()
+      .getOnce("https://api.github.com/", 500);
 
     const octokit = new Octokit({
       request: {
-        fetch: mock,
+        fetch: mock.fetchHandler,
       },
     });
 
@@ -150,7 +152,7 @@ describe("octokit.hook", () => {
           format: "",
         },
         request: {
-          fetch: mock,
+          fetch: mock.fetchHandler,
           hook: requestOptions.request.hook,
         },
       });
diff --git a/test/issues.test.ts b/test/issues.test.ts
index 166de3741..fac727173 100644
--- a/test/issues.test.ts
+++ b/test/issues.test.ts
@@ -15,12 +15,12 @@ import { describe, expect, test } from "vitest";
 describe("issues", () => {
   test("#123 example issue", async () => {
     const mock = fetchMock
-      .sandbox()
+      .createInstance()
       .getOnce("https://api.github.com/", { ok: true });
 
     const octokit = new Octokit({
       request: {
-        fetch: mock,
+        fetch: mock.fetchHandler,
       },
     });
 
diff --git a/test/request.test.ts b/test/request.test.ts
index 2c343c2b1..cbdeb850b 100644
--- a/test/request.test.ts
+++ b/test/request.test.ts
@@ -13,7 +13,7 @@ describe("octokit.request()", () => {
   });
 
   it("GET /", () => {
-    const mock = fetchMock.sandbox().getOnce(
+    const mock = fetchMock.createInstance().getOnce(
       "https://api.github.com/",
       { ok: true },
       {
@@ -26,7 +26,7 @@ describe("octokit.request()", () => {
 
     const octokit = new Octokit({
       request: {
-        fetch: mock,
+        fetch: mock.fetchHandler,
       },
     });
 
@@ -35,13 +35,13 @@ describe("octokit.request()", () => {
 
   it("custom baseUrl", () => {
     const mock = fetchMock
-      .sandbox()
+      .createInstance()
       .getOnce("https://github.acme-inc.com/api/v3/orgs/octokit", { id: 123 });
 
     const octokit = new Octokit({
       baseUrl: "https://github.acme-inc.com/api/v3",
       request: {
-        fetch: mock,
+        fetch: mock.fetchHandler,
       },
     });
 
@@ -51,7 +51,7 @@ describe("octokit.request()", () => {
   });
 
   it("custom user agent", () => {
-    const mock = fetchMock.sandbox().getOnce(
+    const mock = fetchMock.createInstance().getOnce(
       "https://api.github.com/",
       { ok: true },
       {
@@ -65,7 +65,7 @@ describe("octokit.request()", () => {
     const octokit = new Octokit({
       userAgent: "myApp/1.2.3",
       request: {
-        fetch: mock,
+        fetch: mock.fetchHandler,
       },
     });
 
@@ -73,7 +73,7 @@ describe("octokit.request()", () => {
   });
 
   it("custom time zone", () => {
-    const mock = fetchMock.sandbox().getOnce(
+    const mock = fetchMock.createInstance().getOnce(
       "https://api.github.com/",
       { ok: true },
       {
@@ -88,7 +88,7 @@ describe("octokit.request()", () => {
     const octokit = new Octokit({
       timeZone: "Europe/Amsterdam",
       request: {
-        fetch: mock,
+        fetch: mock.fetchHandler,
       },
     });
 
@@ -97,7 +97,7 @@ describe("octokit.request()", () => {
 
   it("previews", async () => {
     const mock = fetchMock
-      .sandbox()
+      .createInstance()
       .getOnce(
         "https://api.github.com/graphql",
         {},
@@ -122,7 +122,7 @@ describe("octokit.request()", () => {
 
     const octokit = new Octokit({
       request: {
-        fetch: mock,
+        fetch: mock.fetchHandler,
       },
     });
 
@@ -159,7 +159,7 @@ describe("octokit.request()", () => {
   });
 
   it("sends null values (octokit/rest.js#765)", () => {
-    const mock = fetchMock.sandbox().patchOnce(
+    const mock = fetchMock.createInstance().patchOnce(
       "https://api.github.com/repos/epmatsw/example-repo/issues/1",
       {},
       {
@@ -172,7 +172,7 @@ describe("octokit.request()", () => {
     const octokit = new Octokit({
       auth: "secret123",
       request: {
-        fetch: mock,
+        fetch: mock.fetchHandler,
       },
     });
     return octokit.request(