diff --git a/lib/wallet.py b/lib/wallet.py
index 104a3c54..55ef493f 100644
--- a/lib/wallet.py
+++ b/lib/wallet.py
@@ -186,6 +186,8 @@ class Wallet:
                 print msg
                 sys.exit(1)
 
+        # This attribute is set when wallet.start_threads is called.
+        self.synchronizer = None
 
         self.load_accounts()