diff -r 16ff5c6066a6 -r 3abba5bc3454 hgext/patchbomb.py
--- a/hgext/patchbomb.py	Tue Jun 13 16:30:50 2017 -0400
+++ b/hgext/patchbomb.py	Tue Jun 13 17:43:33 2017 -0400
@@ -660,15 +660,17 @@
         if addr:
             showaddrs.append('%s: %s' % (header, addr))
             return mail.addrlistencode(ui, [addr], _charsets, opts.get('test'))
-        else:
-            return default
+        elif default:
+            return mail.addrlistencode(
+                ui, [default], _charsets, opts.get('test'))
+        return []
 
     to = getaddrs('To', ask=True)
     if not to:
         # we can get here in non-interactive mode
         raise error.Abort(_('no recipient addresses provided'))
-    cc = getaddrs('Cc', ask=True, default='') or []
-    bcc = getaddrs('Bcc') or []
+    cc = getaddrs('Cc', ask=True, default='')
+    bcc = getaddrs('Bcc')
     replyto = getaddrs('Reply-To')
 
     confirm = ui.configbool('patchbomb', 'confirm')