diff --git a/addressbook/inc/class.addressbook_export_contacts_csv.inc.php b/addressbook/inc/class.addressbook_export_contacts_csv.inc.php
index dd4ef9e797..ad490e0a4c 100644
--- a/addressbook/inc/class.addressbook_export_contacts_csv.inc.php
+++ b/addressbook/inc/class.addressbook_export_contacts_csv.inc.php
@@ -68,7 +68,7 @@ class addressbook_export_contacts_csv implements importexport_iface_export_plugi
 			$this->ui->get_rows($query,$selection,$readonlys, true);	// only return the ids
 		}
 		elseif ( $options['selection'] == 'all' ) {
-			if ($GLOBALS['egw_info']['user']['preferences']['addressbook']['hide_accounts']) {
+			if ($GLOBALS['egw_info']['user']['preferences']['addressbook']['hide_accounts'] === '1') {
 				$col_filter['account_id'] = null;
 			}
 			$selection = ExecMethod2('addressbook.addressbook_bo.search', array(), true, '', '','',false,'AND',false,$col_filter);
diff --git a/addressbook/inc/class.addressbook_export_vcard.inc.php b/addressbook/inc/class.addressbook_export_vcard.inc.php
index 471e8b20f2..91590c6740 100644
--- a/addressbook/inc/class.addressbook_export_vcard.inc.php
+++ b/addressbook/inc/class.addressbook_export_vcard.inc.php
@@ -51,7 +51,7 @@ class addressbook_export_vcard implements importexport_iface_export_plugin {
 			$this->uicontacts->get_rows($query,$this->selection,$readonlys, true);	// only return the ids
 		}
 		elseif ( $options['selection'] == 'all' ) {
-			if ($GLOBALS['egw_info']['user']['preferences']['addressbook']['hide_accounts']) {
+			if ($GLOBALS['egw_info']['user']['preferences']['addressbook']['hide_accounts'] === '1') {
 				$col_filter['account_id'] = null;
 			}
 			$this->selection = ExecMethod2('addressbook.addressbook_bo.search', array(), true, '', '','',false,'AND',false,$col_filter);
diff --git a/addressbook/inc/class.addressbook_groupdav.inc.php b/addressbook/inc/class.addressbook_groupdav.inc.php
index 54793bb6e8..9c85c6bd43 100644
--- a/addressbook/inc/class.addressbook_groupdav.inc.php
+++ b/addressbook/inc/class.addressbook_groupdav.inc.php
@@ -123,7 +123,7 @@ class addressbook_groupdav extends Api\CalDAV\Handler
 			$filter['owner'] = $user;
 		}
 		// should we hide the accounts addressbook
-		if ($GLOBALS['egw_info']['user']['preferences']['addressbook']['hide_accounts']) $filter['account_id'] = null;
+		if ($GLOBALS['egw_info']['user']['preferences']['addressbook']['hide_accounts'] === '1') $filter['account_id'] = null;
 
 		// process REPORT filters or multiget href's
 		$nresults = null;
@@ -1076,7 +1076,7 @@ class addressbook_groupdav extends Api\CalDAV\Handler
 		}
 		foreach(array_keys($this->bo->get_addressbooks(Acl::READ)) as $id)
 		{
-			if (($id || !$GLOBALS['egw_info']['user']['preferences']['addressbook']['hide_accounts']) &&
+			if (($id || $GLOBALS['egw_info']['user']['preferences']['addressbook']['hide_accounts'] !== '1') &&
 				$GLOBALS['egw_info']['user']['account_id'] != $id &&	// no current user and no accounts, if disabled in ab prefs
 				(in_array('A',$this->home_set_pref) || in_array((string)$id,$this->home_set_pref)) &&
 				is_numeric($id) && ($owner = $id ? $this->accounts->id2name($id) : 'accounts'))
@@ -1101,7 +1101,7 @@ class addressbook_groupdav extends Api\CalDAV\Handler
 			Api\CalDAV::mkprop('href',$data['caldav']->base_uri.'/'.$GLOBALS['egw_info']['user']['account_lid'].'/')));
 
 		$data['props']['principal-address'] = Api\CalDAV::mkprop(Api\CalDAV::CARDDAV, 'principal-address',
-				$GLOBALS['egw_info']['user']['preferences']['addressbook']['hide_accounts'] ? '' : array(
+				$GLOBALS['egw_info']['user']['preferences']['addressbook']['hide_accounts'] === '1' ? '' : array(
 				Api\CalDAV::mkprop('href',$data['caldav']->base_uri.'/addressbook-accounts/'.$GLOBALS['egw_info']['user']['person_id'].'.vcf')));
 
 		$data['props']['directory-gateway'] = Api\CalDAV::mkprop(Api\CalDAV::CARDDAV, 'directory-gateway', array(
@@ -1141,7 +1141,7 @@ class addressbook_groupdav extends Api\CalDAV\Handler
 		// rewriting owner=0 to 'U', as 0 get's always selected by prefs
 		// not removing it for default or forced prefs based on current users pref
 		if (!isset($addressbooks[0]) && (in_array($hook_data['type'], array('user', 'group')) ||
-			$GLOBALS['egw_info']['user']['preferences']['addressbook']['hide_accounts']))
+			$GLOBALS['egw_info']['user']['preferences']['addressbook']['hide_accounts'] === '1'))
 		{
 			unset($addressbooks['U']);
 		}
diff --git a/addressbook/inc/class.addressbook_zpush.inc.php b/addressbook/inc/class.addressbook_zpush.inc.php
index 580682b4ed..110c239b94 100644
--- a/addressbook/inc/class.addressbook_zpush.inc.php
+++ b/addressbook/inc/class.addressbook_zpush.inc.php
@@ -869,7 +869,7 @@ class addressbook_zpush implements activesync_plugin_write, activesync_plugin_se
 		// rewriting owner=0 to 'U', as 0 get's always selected by prefs
 		// not removing it for default or forced prefs based on current users pref
 		if (!isset($addressbooks[0]) && (in_array($hook_data['type'], array('user', 'group')) ||
-			$GLOBALS['egw_info']['user']['preferences']['addressbook']['hide_accounts']))
+			$GLOBALS['egw_info']['user']['preferences']['addressbook']['hide_accounts'] === '1'))
 		{
 			unset($addressbooks['U']);
 		}
diff --git a/api/src/CalDAV.php b/api/src/CalDAV.php
index 0f352df294..d47f0f7530 100644
--- a/api/src/CalDAV.php
+++ b/api/src/CalDAV.php
@@ -675,7 +675,7 @@ class CalDAV extends HTTP_WebDAV_Server
 
 				// only add global /addressbook-accounts/ as the one in home-set is added (and controled) by add_shared
 				if ($path == '/' && $app == 'addressbook' &&
-					!$GLOBALS['egw_info']['user']['preferences']['addressbook']['hide_accounts'])
+					$GLOBALS['egw_info']['user']['preferences']['addressbook']['hide_accounts'] !== '1')
 				{
 					$file = $this->add_app($app,false,0,$path.$app.'-accounts/');
 					$file['props']['resourcetype']['val'][] = self::mkprop(self::CALENDARSERVER,'shared','');
@@ -851,7 +851,7 @@ class CalDAV extends HTTP_WebDAV_Server
 					$props['displayname'] = lang('All addressbooks');
 					break;
 				}
-				elseif(!$user && !$GLOBALS['egw_info']['user']['preferences']['addressbook']['hide_accounts'])
+				elseif(!$user && $GLOBALS['egw_info']['user']['preferences']['addressbook']['hide_accounts'] !== '1')
 				{
 					unset($props['owner']);
 					$props['displayname'] = lang($app).' '.lang('Accounts');
@@ -1972,7 +1972,7 @@ class CalDAV extends HTTP_WebDAV_Server
 		{
 			$user_prefix = '/'.$GLOBALS['egw_info']['user']['account_lid'].'/'.$app;
 			list($app, $username) = explode('-', $app, 2);
-			if ($username == 'accounts' && !$GLOBALS['egw_info']['user']['preferences']['addressbook']['hide_accounts'])
+			if ($username == 'accounts' && $GLOBALS['egw_info']['user']['preferences']['addressbook']['hide_accounts'] !== '1')
 			{
 				$account_id = 0;
 			}
diff --git a/api/src/CalDAV/Principals.php b/api/src/CalDAV/Principals.php
index ffa77d87cb..d59ca38a71 100644
--- a/api/src/CalDAV/Principals.php
+++ b/api/src/CalDAV/Principals.php
@@ -983,7 +983,7 @@ class Principals extends Handler
 			// CardDAV
 			'addressbook-home-set' => Api\CalDAV::mkprop(Api\CalDAV::CARDDAV,'addressbook-home-set',$addressbooks),
 			'principal-address' => Api\CalDAV::mkprop(Api\CalDAV::CARDDAV,'principal-address',
-				$GLOBALS['egw_info']['user']['preferences']['addressbook']['hide_accounts'] ? '' : array(
+				$GLOBALS['egw_info']['user']['preferences']['addressbook']['hide_accounts'] === '1' ? '' : array(
 				Api\CalDAV::mkprop('href',$this->base_uri.'/addressbook-accounts/'.$account['person_id'].'.vcf'))),
 			// CardDAV directory
 			'directory-gateway' => Api\CalDAV::mkprop(Api\CalDAV::CARDDAV, 'directory-gateway',array(
diff --git a/api/src/Contacts.php b/api/src/Contacts.php
index 12d421b747..20269b7816 100755
--- a/api/src/Contacts.php
+++ b/api/src/Contacts.php
@@ -1550,7 +1550,7 @@ class Contacts extends Contacts\Storage
 			$limit = array($options['start'], $options['num_rows']);
 		}
 		$filter = (array)$options['filter'];
-		if ($GLOBALS['egw_info']['user']['preferences']['addressbook']['hide_accounts']) $filter['account_id'] = null;
+		if ($GLOBALS['egw_info']['user']['preferences']['addressbook']['hide_accounts'] === '1') $filter['account_id'] = null;
 		if (($contacts =& parent::search($criteria,false,'org_name,n_family,n_given,cat_id,contact_email','','%',false,'OR', $limit, $filter)))
 		{
 			$ids = array();
@@ -2508,7 +2508,7 @@ class Contacts extends Contacts\Storage
 		if (!is_null($owner)) $filter['owner'] = $owner;
 
 		// should we hide the accounts addressbook
-		if (!$owner && $GLOBALS['egw_info']['user']['preferences']['addressbook']['hide_accounts'])
+		if (!$owner && $GLOBALS['egw_info']['user']['preferences']['addressbook']['hide_accounts'] === '1')
 		{
 			$filter['account_id'] = null;
 		}
diff --git a/api/src/Contacts/Storage.php b/api/src/Contacts/Storage.php
index 40afd4ac31..0522c104f2 100755
--- a/api/src/Contacts/Storage.php
+++ b/api/src/Contacts/Storage.php
@@ -1165,7 +1165,7 @@ class Storage
 		}
 
 		// add groups for all backends, if accounts addressbook is not hidden
-		if (empty($GLOBALS['egw_info']['user']['preferences']['addressbook']['hide_accounts']))
+		if ($GLOBALS['egw_info']['user']['preferences']['addressbook']['hide_accounts'] !== '1')
 		{
 			foreach($GLOBALS['egw']->accounts->search(array(
 				'type' => 'groups'
diff --git a/home/inc/class.home_birthday_portlet.inc.php b/home/inc/class.home_birthday_portlet.inc.php
index 1c52e161cd..077219eabe 100644
--- a/home/inc/class.home_birthday_portlet.inc.php
+++ b/home/inc/class.home_birthday_portlet.inc.php
@@ -92,7 +92,7 @@ use EGroupware\Api\Etemplate;
 		$bdays =& $contacts->search(array('bday' => $month_start),array('id','n_family','n_given','bday'),'n_given,n_family','','%');
 		// search accounts too, if not stored in accounts repository
 		$extra_accounts_search = $contacts->account_repository == 'ldap' && !is_null($contacts->so_accounts) &&
-			!$GLOBALS['egw_info']['user']['preferences']['addressbook']['hide_accounts'];
+			$GLOBALS['egw_info']['user']['preferences']['addressbook']['hide_accounts'] !== '1';
 		if ($extra_accounts_search && ($bdays2 = $contacts->search(array('bday' => $month_start),array('id','n_family','n_given','bday'),
 			'n_given,n_family','','%',false,'AND',false,array('owner' => 0))))
 		{
diff --git a/mail/inc/class.mail_compose.inc.php b/mail/inc/class.mail_compose.inc.php
index f11671417d..50ba6ff57b 100644
--- a/mail/inc/class.mail_compose.inc.php
+++ b/mail/inc/class.mail_compose.inc.php
@@ -883,7 +883,7 @@ class mail_compose
 							{
 								$_searchCond = array('contact_id'=>$addressArray);
 								//error_log(__METHOD__.__LINE__.$_searchString);
-								if ($GLOBALS['egw_info']['user']['preferences']['addressbook']['hide_accounts']) $showAccounts=false;
+								$showAccounts= $GLOBALS['egw_info']['user']['preferences']['addressbook']['hide_accounts'] !== '1';
 								$filter = ($showAccounts?array():array('account_id' => null));
 								$filter['cols_to_search']=array('n_fn','email','email_home');
 								$contacts = $contacts_obj->search($_searchCond,array('n_fn','email','email_home'),'n_fn','','%',false,'OR',array(0,100),$filter);
@@ -3483,7 +3483,7 @@ class mail_compose
 		if ($GLOBALS['egw_info']['user']['apps']['addressbook'] && strlen($_searchString)>=$_searchStringLength)
 		{
 			//error_log(__METHOD__.__LINE__.array2string($_searchString));
-			$showAccounts = empty($GLOBALS['egw_info']['user']['preferences']['addressbook']['hide_accounts']);
+			$showAccounts = $GLOBALS['egw_info']['user']['preferences']['addressbook']['hide_accounts'] !== '1';
 			$search = explode(' ', $_searchString);
 			foreach ($search as $k => $v)
 			{