diff --git a/src/client.ts b/src/client.ts
index f9951e2..33a275e 100644
--- a/src/client.ts
+++ b/src/client.ts
@@ -12,10 +12,20 @@ export const signUp = async (payload: SignUpPayload): Promise<User> => {
     method: 'POST',
     body: JSON.stringify(payload),
     headers: {
-      'Content-Type': 'application/json'
+      'Content-Type': 'application/json; charset=UTF-8'
     }
   });
 
+  if (!res.ok) {
+    const isJson = res.headers
+      .get('Content-Type')
+      ?.includes('application/json');
+
+    const data = isJson ? await res.json() : await res.text();
+
+    throw new Error(data);
+  }
+
   const user = await res.json();
 
   return user;