diff --git a/client/gui.py b/client/gui.py
index 64226cbaa..c8b689772 100644
--- a/client/gui.py
+++ b/client/gui.py
@@ -592,7 +592,10 @@ class BitcoinGUI:
                     old_r = r
                     r = r.strip()
                     if re.match('^(|([\w\-\.]+)@)((\w[\w\-]+\.)+[\w\-]+)$', r):
-                        to_address = self.wallet.get_alias(r)
+                        try:
+                            to_address = self.wallet.get_alias(r)
+                        except:
+                            continue
                         if to_address:
                             s = r + ' <' + to_address + '>'
                             gobject.idle_add( lambda: self.payto_entry.set_text(s) )
@@ -780,6 +783,9 @@ class BitcoinGUI:
         if signature:
             try:
                 signing_address = self.wallet.get_alias(identity)
+            except:
+                self.show_message('Warning: the key of the recipient has changed since last visit.\nContinue at your own risks!')
+            try:
                 self.wallet.verify_message(signing_address, signature, cmd )
             except:
                 self.show_message('Warning: the URI contains a bad signature.\nThe identity of the recipient cannot be verified.\nContinue at your own risks!')
@@ -821,6 +827,15 @@ class BitcoinGUI:
         payto_entry, label_entry, amount_entry, fee_entry = data
         label = label_entry.get_text()
         r = payto_entry.get_text()
+
+        r = r.strip()
+        if re.match('^(|([\w\-\.]+)@)((\w[\w\-]+\.)+[\w\-]+)$', r):
+            try:
+                to_address = self.wallet.get_alias(r)
+            except:
+                self.show_message('Warning: the key of the recipient has changed since last visit.')
+                return
+
         m = re.match('(|([\w\-\.]+)@)((\w[\w\-]+\.)+[\w\-]+) \<([1-9A-HJ-NP-Za-km-z]{26,})\>', r)
         if m:
             to_address = m.group(5)
diff --git a/client/wallet.py b/client/wallet.py
index c8881c1a8..f984c8ce5 100644
--- a/client/wallet.py
+++ b/client/wallet.py
@@ -237,6 +237,7 @@ class Wallet:
         self.status = {}             # current status of addresses
         self.history = {}
         self.labels = {}             # labels for addresses and transactions
+        self.aliases = {}            # aliases for addresses
         self.addressbook = []        # outgoing addresses, for payments
 
         # not saved
@@ -475,6 +476,7 @@ class Wallet:
             'labels':self.labels,
             'contacts':self.addressbook,
             'imported_keys':self.imported_keys,
+            'aliases':self.aliases,
             }
         f = open(self.path,"w")
         f.write( repr(s) )
@@ -505,6 +507,7 @@ class Wallet:
             self.labels = d.get('labels')
             self.addressbook = d.get('contacts')
             self.imported_keys = d.get('imported_keys',{})
+            self.aliases = d.get('aliases',{})
         except:
             raise BaseException(upgrade_msg)
 
@@ -725,4 +728,13 @@ class Wallet:
                 return ''
             if not self.is_valid(xx):
                 return ''
+            self.labels[xx] = x
+
+            s = self.aliases.get(x)
+            if s:
+                if s != xx:
+                    raise BaseException("error:alias does not match previous value")
+            else:
+                self.aliases[x] = xx
+            
             return xx