diff --git a/lib/RevBank/Users.pm b/lib/RevBank/Users.pm
index 31f3c4d..227b6ce 100644
--- a/lib/RevBank/Users.pm
+++ b/lib/RevBank/Users.pm
@@ -134,7 +134,7 @@ sub assert_user($username) {
     my $user = $users->{ lc $username };
 
     if ($user) {
-        Carp::croak("Account $username can't be used") if not balance $username;
+        Carp::croak("Account $username can't be used") if not defined balance $username;
         return $user->[0];
     }
 
diff --git a/revbank b/revbank
index 2ea3379..16390df 100755
--- a/revbank
+++ b/revbank
@@ -16,7 +16,7 @@ use RevBank::Messages;
 use RevBank::Cart;
 use RevBank::Prompt;
 
-our $VERSION = "6.1.3";
+our $VERSION = "6.1.4";
 our %HELP1 = (
     "abort" => "Abort the current transaction",
 );