diff --git a/src/app/admin/import/sync/sync-all-client.tsx b/src/app/admin/import/sync/sync-all-client.tsx
index 2f789fa5..3eba9b0b 100644
--- a/src/app/admin/import/sync/sync-all-client.tsx
+++ b/src/app/admin/import/sync/sync-all-client.tsx
@@ -46,6 +46,19 @@ export function SyncAllClient() {
 				return;
 			}
 
+			if (!res.headers.get("content-type")?.includes("text/event-stream")) {
+				let errMsg = "Sync failed";
+				try {
+					const json = await res.json();
+					errMsg = json.error || errMsg;
+				} catch {
+					// ignore
+				}
+				toast.error(errMsg);
+				setSyncing(false);
+				return;
+			}
+
 			const reader = res.body.getReader();
 			const decoder = new TextDecoder();
 			let buf = "";