diff --git a/discojs/src/client/client.ts b/discojs/src/client/client.ts
index 9f05febc7..795f9346e 100644
--- a/discojs/src/client/client.ts
+++ b/discojs/src/client/client.ts
@@ -178,6 +178,8 @@ export abstract class Client extends EventEmitter<{'status': RoundStatus}>{
     url.pathname += `tasks/${this.task.id}/model.json`
 
     const response = await fetch(url);
+    if (!response.ok) throw new Error(`fetch: HTTP status ${response.status}`);
+
     const encoded = new Uint8Array(await response.arrayBuffer())
     return await serialization.model.decode(encoded)
   }
diff --git a/discojs/src/task/task_handler.ts b/discojs/src/task/task_handler.ts
index 7b38a6928..d2b692bb4 100644
--- a/discojs/src/task/task_handler.ts
+++ b/discojs/src/task/task_handler.ts
@@ -20,7 +20,7 @@ export async function pushTask<D extends DataType>(
   task: Task<D>,
   model: Model<D>,
 ): Promise<void> {
-  await fetch(urlToTasks(base), {
+  const response = await fetch(urlToTasks(base), {
     method: "POST",
     body: JSON.stringify({
       task,
@@ -28,12 +28,14 @@ export async function pushTask<D extends DataType>(
       weights: await serialization.weights.encode(model.weights),
     }),
   });
+  if (!response.ok) throw new Error(`fetch: HTTP status ${response.status}`);
 }
 
 export async function fetchTasks(
   base: URL,
 ): Promise<Map<TaskID, Task<DataType>>> {
   const response = await fetch(urlToTasks(base));
+  if (!response.ok) throw new Error(`fetch: HTTP status ${response.status}`);
   const tasks: unknown = await response.json();
 
   if (!Array.isArray(tasks)) {
diff --git a/webapp/src/components/testing/__tests__/Testing.spec.ts b/webapp/src/components/testing/__tests__/Testing.spec.ts
index 7cd5d62dd..341cfc129 100644
--- a/webapp/src/components/testing/__tests__/Testing.spec.ts
+++ b/webapp/src/components/testing/__tests__/Testing.spec.ts
@@ -60,7 +60,7 @@ it("shows stored models", async () => {
 it("allows to download server's models", async () => {
   vi.stubGlobal("fetch", async (url: string | URL) => {
     if (url.toString() === "http://localhost:8080/tasks")
-      return { json: () => Promise.resolve([TASK]) };
+      return new Response(JSON.stringify([TASK]));
     throw new Error(`unhandled get: ${url}`);
   });
   afterEach(() => {
diff --git a/webapp/src/components/training/__tests__/Trainer.spec.ts b/webapp/src/components/training/__tests__/Trainer.spec.ts
index b77d27493..5dfd74762 100644
--- a/webapp/src/components/training/__tests__/Trainer.spec.ts
+++ b/webapp/src/components/training/__tests__/Trainer.spec.ts
@@ -10,39 +10,15 @@ import { loadCSV } from "@epfml/discojs-web";
 import Trainer from "../Trainer.vue";
 import TrainingInformation from "../TrainingInformation.vue";
 
-vi.mock("axios", async () => {
-  async function get(url: string) {
-    if (url === "http://localhost:8080/tasks/titanic/model.json") {
-      return {
-        data: await serialization.model.encode(
-          await defaultTasks.titanic.getModel(),
-        ),
-      };
-    }
-    throw new Error("unhandled get");
-  }
-
-  const axios = await vi.importActual<typeof import("axios")>("axios");
-  return {
-    ...axios,
-    default: {
-      ...axios.default,
-      get,
-    },
-  };
-});
-
 async function setupForTask() {
   const provider = defaultTasks.titanic;
 
   vi.stubGlobal("fetch", async (url: string | URL) => {
-    if (url.toString() === "http://localhost:8080/tasks/titanic/model.json")
-      return {
-        arrayBuffer: async () => {
-          const model = await provider.getModel();
-          return await serialization.model.encode(model);
-        },
-      };
+    if (url.toString() === "http://localhost:8080/tasks/titanic/model.json") {
+      const model = await provider.getModel();
+      const encoded = await serialization.model.encode(model);
+      return new Response(encoded);
+    }
     throw new Error(`unhandled get: ${url}`);
   });
   afterEach(() => {