diff --git a/config/example-config.php b/config/example-config.php
index b19eb93b..47adc43e 100644
--- a/config/example-config.php
+++ b/config/example-config.php
@@ -171,6 +171,17 @@ $c->admin_email ='calendar-admin@example.com';
 // $c->home_calendar_name = 'calendar';
 // $c->home_addressbook_name = 'addresses';
 
+/**
+* Sets a numeric value indicating the maximum size in octets (bytes) of a resource
+* that the server is willing to accept when an address object resource is stored
+* in an address book collection (e.g. contacts with image attachments).
+* Note that not all clients respect that property and that DAViCal won't deny creating
+* or updating a resource that is larger than the specified limit if the client willingly or
+* unwillingly ignores that property. Currently (late 2018) we only know of iOS devices to handle it properly.
+* Default: 6550000
+*/
+// $c->carddav_max_resource_size = 6550000;
+
 /**
 * If the above options are not suitable for your new users, use this to create
 * a more complex default collection management.
diff --git a/htdocs/always.php b/htdocs/always.php
index b4de04e0..f32b0b9d 100644
--- a/htdocs/always.php
+++ b/htdocs/always.php
@@ -83,6 +83,7 @@ $c->permission_scan_depth = 2;
 $c->expand_pdo_parameters = true;
 $c->home_calendar_name    = 'calendar';
 $c->home_addressbook_name = 'addresses';
+$c->carddav_max_resource_size = 6550000;
 $c->enable_row_linking = true;
 $c->enable_scheduling = false;
 $c->http_auth_mode = 'Basic';
diff --git a/inc/DAVResource.php b/inc/DAVResource.php
index 4b34cee1..f6220b27 100644
--- a/inc/DAVResource.php
+++ b/inc/DAVResource.php
@@ -1842,7 +1842,7 @@ EOQRY;
 
       case 'urn:ietf:params:xml:ns:carddav:max-resource-size':
         if ( ! $this->_is_collection || !$this->_is_addressbook ) return false;
-        $reply->NSElement($prop, $tag, '' );
+        $reply->NSElement($prop, $tag, $c->carddav_max_resource_size );
         break;
 
       case 'urn:ietf:params:xml:ns:carddav:supported-address-data':
diff --git a/inc/always.php.in b/inc/always.php.in
index e511655a..3f151df0 100644
--- a/inc/always.php.in
+++ b/inc/always.php.in
@@ -83,6 +83,7 @@ $c->permission_scan_depth = 2;
 $c->expand_pdo_parameters = true;
 $c->home_calendar_name    = 'calendar';
 $c->home_addressbook_name = 'addresses';
+$c->carddav_max_resource_size = 6550000;
 $c->enable_row_linking = true;
 $c->enable_scheduling = false;
 $c->http_auth_mode = 'Basic';