diff --git a/client/wallet.py b/client/wallet.py
index aaf3fbb6..331604f1 100644
--- a/client/wallet.py
+++ b/client/wallet.py
@@ -287,6 +287,7 @@ class Wallet:
     def import_key(self, keypair, password):
         address, key = keypair.split(':')
         if not self.is_valid(address): return False
+        if address in self.all_addresses(): return False
         b = ASecretToSecret( key )
         if not b: return False
         secexp = int( b.encode('hex'), 16)