diff --git a/components/KeyManagementManager.tsx b/components/KeyManagementManager.tsx
index 6fc80f5..c3caee1 100644
--- a/components/KeyManagementManager.tsx
+++ b/components/KeyManagementManager.tsx
@@ -94,13 +94,18 @@ export function KeyManagementManager() {
     try {
       // Try to decode as nsec
       const decoded = nip19.decode(extractedKey)
-      if (decoded.type !== 'nsec' || typeof decoded.data !== 'string') {
+      if (decoded.type !== 'nsec') {
         throw new Error('Invalid nsec format')
       }
-    } catch {
-      // Assume it's hex, validate length (64 hex chars = 32 bytes)
+      // decoded.data can be string (hex) or Uint8Array, both are valid
+      if (typeof decoded.data !== 'string' && !(decoded.data instanceof Uint8Array)) {
+        throw new Error('Invalid nsec format')
+      }
+    } catch (e) {
+      // If decoding failed, assume it's hex, validate length (64 hex chars = 32 bytes)
       if (!/^[0-9a-f]{64}$/i.test(extractedKey)) {
-        setError('Invalid key format. Please provide a nsec (nsec1...) or hex (64 characters) private key.')
+        const errorMsg = e instanceof Error ? e.message : 'Invalid format'
+        setError(`Invalid key format: ${errorMsg}. Please provide a nsec (nsec1...) or hex (64 characters) private key.`)
         return
       }
     }
diff --git a/lib/keyManagement.ts b/lib/keyManagement.ts
index b471dee..7272744 100644
--- a/lib/keyManagement.ts
+++ b/lib/keyManagement.ts
@@ -39,8 +39,15 @@ export class KeyManagementService {
     // Try to decode as nsec
     try {
       const decoded = nip19.decode(privateKey)
-      if (decoded.type === 'nsec' && typeof decoded.data === 'string') {
-        privateKeyHex = decoded.data
+      if (decoded.type === 'nsec') {
+        // decoded.data can be string (hex) or Uint8Array depending on nostr-tools version
+        if (typeof decoded.data === 'string') {
+          privateKeyHex = decoded.data
+        } else if (decoded.data instanceof Uint8Array) {
+          privateKeyHex = bytesToHex(decoded.data)
+        } else {
+          throw new Error('Invalid nsec format: data is neither string nor Uint8Array')
+        }
       } else {
         throw new Error('Invalid nsec format')
       }