diff --git a/proxy/mailing/confirm.php b/proxy/mailing/confirm.php
index 10f2fe1..e62a989 100644
--- a/proxy/mailing/confirm.php
+++ b/proxy/mailing/confirm.php
@@ -19,7 +19,7 @@ civiproxy_security_check('mail-confirm');
 // basic restraints
 $valid_parameters = array(    'sid'          => 'int',
                               'cid'          => 'int', 
-                              'h'            => 'hex');
+                              'h'            => 'string');
 $parameters = civiproxy_get_parameters($valid_parameters);
 
 // check if parameters specified
diff --git a/proxy/mailing/resubscribe.php b/proxy/mailing/resubscribe.php
index 347e491..10c4900 100644
--- a/proxy/mailing/resubscribe.php
+++ b/proxy/mailing/resubscribe.php
@@ -19,7 +19,7 @@ civiproxy_security_check('mail-resubscribe');
 // basic restraints
 $valid_parameters = array(    'jid'          => 'int',
                               'qid'          => 'int', 
-                              'h'            => 'hex');
+                              'h'            => 'string');
 $parameters = civiproxy_get_parameters($valid_parameters);
 
 // check if parameters specified
diff --git a/proxy/mailing/unsubscribe.php b/proxy/mailing/unsubscribe.php
index 6ffca5c..b5763e8 100644
--- a/proxy/mailing/unsubscribe.php
+++ b/proxy/mailing/unsubscribe.php
@@ -19,7 +19,7 @@ civiproxy_security_check('mail-unsubscribe');
 // basic restraints
 $valid_parameters = array(    'jid'          => 'int',
                               'qid'          => 'int', 
-                              'h'            => 'hex');
+                              'h'            => 'string');
 $parameters = civiproxy_get_parameters($valid_parameters);
 
 // check if parameters specified