diff --git a/src/actions/compose.ts b/src/actions/compose.ts
index 7bce18894..0c3bd2a68 100644
--- a/src/actions/compose.ts
+++ b/src/actions/compose.ts
@@ -384,7 +384,10 @@ const uploadCompose = (composeId: string, files: FileList, intl: IntlShape) =>
         f,
         intl,
         (data) => dispatch(uploadComposeSuccess(composeId, data, f)),
-        (error) => dispatch(uploadComposeFail(composeId, error)),
+        (error) => {
+          console.error(error);
+          dispatch(uploadComposeFail(composeId, error));
+        },
         (e: ProgressEvent) => {
           progress[i] = e.loaded;
           dispatch(uploadComposeProgress(composeId, progress.reduce((a, v) => a + v, 0), e.total));
diff --git a/src/api/MastodonResponse.ts b/src/api/MastodonResponse.ts
index b85fe7c49..6bd1a1ace 100644
--- a/src/api/MastodonResponse.ts
+++ b/src/api/MastodonResponse.ts
@@ -81,7 +81,7 @@ export class MastodonResponse extends Response {
         z.string(),
         z.object({ error: z.string(), description: z.string() }).array(),
       ).optional(),
-    });
+    }).passthrough();
   }
 
 }
diff --git a/src/main.tsx b/src/main.tsx
index 9204d45bd..61ef3b99a 100644
--- a/src/main.tsx
+++ b/src/main.tsx
@@ -1,3 +1,5 @@
+import 'soapbox/polyfill/Promise.withResolvers.ts';
+
 import { enableMapSet } from 'immer';
 import { createRoot } from 'react-dom/client';
 
diff --git a/src/polyfill/Promise.withResolvers.ts b/src/polyfill/Promise.withResolvers.ts
new file mode 100644
index 000000000..918bf4504
--- /dev/null
+++ b/src/polyfill/Promise.withResolvers.ts
@@ -0,0 +1,14 @@
+if (!Promise.withResolvers) {
+  Promise.withResolvers = function withResolvers<T>(): PromiseWithResolvers<T> {
+
+    let resolve: (value: T | PromiseLike<T>) => void;
+    let reject: (reason?: any) => void;
+
+    const promise = new this<T>((_resolve, _reject) => {
+      resolve = _resolve;
+      reject = _reject;
+    });
+
+    return { resolve: resolve!, reject: reject!, promise };
+  };
+}
\ No newline at end of file
diff --git a/src/toast.tsx b/src/toast.tsx
index 3011a9b87..ee2e4d6ae 100644
--- a/src/toast.tsx
+++ b/src/toast.tsx
@@ -57,9 +57,13 @@ async function showAlertForError(networkError: HTTPError): Promise<void> {
       return;
     }
 
-    const data = await response.error();
-    if (data) {
-      return error(data.error);
+    try {
+      const data = await response.error();
+      if (data) {
+        return error(data.error);
+      }
+    } catch {
+      // fallthrough
     }
 
     const message = httpErrorMessages.find((httpError) => httpError.code === status)?.description;