diff --git a/src/private-wrap.ts b/src/private-wrap.ts
index ae9925e..d6b1821 100644
--- a/src/private-wrap.ts
+++ b/src/private-wrap.ts
@@ -39,12 +39,19 @@ export class PrivateWrap {
     const box = this.box.toString()
     return `${pubkey}.${box}`
   }
-  public static async fromString(data: string): Promise<PrivateWrap> {
+  public static async fromString(data: string): Promise<PrivateWrap | null> {
     log.trace('fromString')
+
     const parts = data.split('.', 2)
-    const pubkey_str = b642a(parts[0]).expect('Failed to decode pubkey')
-    const pubkey = await crypto.subtle.importKey('spki', pubkey_str, algorithm, true, [])
+    if (parts.length !== 2) return null
+
+    const pubkey_str = b642a(parts[0])
+    if (pubkey_str.is_err()) return null
+    const pubkey = await crypto.subtle.importKey('spki', pubkey_str.unwrap(), algorithm, true, [])
+
     const box = SecretWrap.fromString(parts[1])
+    if (box === null) return null
+
     return new PrivateWrap(box, pubkey)
   }
 }