diff --git a/CRM/Twingle/Submission.php b/CRM/Twingle/Submission.php
index b96c64e..2c2a282 100644
--- a/CRM/Twingle/Submission.php
+++ b/CRM/Twingle/Submission.php
@@ -200,6 +200,14 @@ class CRM_Twingle_Submission {
       }
     }
 
+    // Prepare values: language.
+    if (!empty($contact_data['preferred_language'])) {
+      $mapping = CRM_Core_I18n_PseudoConstant::longForShortMapping();
+      // Override the default mapping for German.
+      $mapping['de'] = 'de_DE';
+      $contact_data['preferred_language'] = $mapping[$contact_data['preferred_language']];
+    }
+
     // Pass to XCM.
     $contact_data['contact_type'] = $contact_type;
     $contact = civicrm_api3('Contact', 'getorcreate', $contact_data);
diff --git a/README.md b/README.md
index 0e2e580..9b4fec0 100644
--- a/README.md
+++ b/README.md
@@ -113,10 +113,11 @@ The action accepts the following parameters:
 | <nobr>`user_street`</nobr>             | String  | The street address of the contact                                                   |                                                                                                                                                                                                                                                                                                                                                                                                                               |                                                                 |
 | <nobr>`user_postal_code`</nobr>        | String  | The postal code of the contact                                                      |                                                                                                                                                                                                                                                                                                                                                                                                                               |                                                                 |
 | <nobr>`user_city`</nobr>               | String  | The city of the contact                                                             |                                                                                                                                                                                                                                                                                                                                                                                                                               |                                                                 |
-| <nobr>`user_country`</nobr>            | String  | The country of the contact                                                          | [ISO 3166-1 Alpha-2 country codes](https://en.wikipedia.org/wiki/ISO_3166-1_alpha-2#Officially_assigned_code_elements)                                                                                                                                                                                                                                                                                                        |                                                                 |
+| <nobr>`user_country`</nobr>            | String  | The country of the contact                                                          | A [ISO 3166-1 Alpha-2 country code](https://en.wikipedia.org/wiki/ISO_3166-1_alpha-2#Officially_assigned_code_elements)                                                                                                                                                                                                                                                                                                       |                                                                 |
 | <nobr>`user_telephone`</nobr>          | String  | The telephone number of the contact                                                 |                                                                                                                                                                                                                                                                                                                                                                                                                               |                                                                 |
 | <nobr>`user_company`</nobr>            | String  | The company of the contact                                                          |                                                                                                                                                                                                                                                                                                                                                                                                                               |                                                                 |
 | <nobr>`user_extrafield`</nobr>         | String  | Additional information of the contact                                               |                                                                                                                                                                                                                                                                                                                                                                                                                               |                                                                 |
+| <nobr>`user_language`</nobr>           | String  | The preferred language of the contact.                                              | A [ISO-639-1 2-digit language code](https://en.wikipedia.org/wiki/List_of_ISO_639-1_codes)                                                                                                                                                                                                                                                                                                                                    |                                                                 |
 | <nobr>`campaign_id`</nobr>             | Integer | The CiviCRM ID of a campaign to assign the contribution                             | A valid CiviCRM Campaign ID. This overrides the campaign ID configured within the profile.                                                                                                                                                                                                                                                                                                                                    |                                                                 |
 
 You may also refer to
diff --git a/api/v3/TwingleDonation/Submit.php b/api/v3/TwingleDonation/Submit.php
index 4025f97..abea337 100644
--- a/api/v3/TwingleDonation/Submit.php
+++ b/api/v3/TwingleDonation/Submit.php
@@ -224,6 +224,13 @@ function _civicrm_api3_twingle_donation_Submit_spec(&$params) {
     'api.required' => 0,
     'description'  => E::ts('The company of the contact.'),
   );
+  $params['user_language'] = array(
+    'name'         => 'user_language',
+    'title'        => E::ts('Language'),
+    'type'         => CRM_Utils_Type::T_STRING,
+    'api.required' => 0,
+    'description'  => E::ts('The preferred language of the contact. A 2-digit ISO-639-1 language code.'),
+  );
   $params['user_extrafield'] = array(
     'name'         => 'user_extrafield',
     'title'        => E::ts('User extra field'),
@@ -393,6 +400,7 @@ function civicrm_api3_twingle_donation_Submit($params) {
                  'user_birthdate' => 'birth_date',
                  'user_email' => 'email',
                  'user_telephone' => 'phone',
+                 'user_language' => 'preferred_language',
                  'user_title' => 'formal_title',
                  'debit_iban' => 'iban',
                ) as $contact_param => $contact_component) {