diff --git a/payment_donation.module b/payment_donation.module
index f862084..20c6958 100644
--- a/payment_donation.module
+++ b/payment_donation.module
@@ -93,6 +93,23 @@ function payment_donation_block_view($delta = '') {
 }
 
 /**
+ * Implements hook_field_extra_fields().
+ */
+function payment_donation_field_extra_fields() {
+  $fields['payment']['payment'] = array(
+    'form' => array(
+      'payment_donation_amount' => array(
+        'label' => t('Payment amount (Payment donation form)'),
+        'description' => '',
+        'weight' => 99,
+      ),
+    ),
+  );
+
+  return $fields;
+}
+
+/**
  * Implements form build callback: the donation form.
  */
 function payment_donation_form(array $form, array &$form_state) {
@@ -108,17 +125,17 @@ function payment_donation_form(array $form, array &$form_state) {
 
   $payment_method = entity_load_single('payment_method', $pmid);
 
-  $form['amount'] = array(
+  $form['payment_donation_amount'] = array(
     '#currency_code' => $currency_code,
     '#title' => t('Amount'),
     '#type' => 'currency_amount',
   );
   $currencies = $payment_method->controller->currencies;
   if (isset($currencies[$currency_code]['minimum'])) {
-    $form['amount']['#minimum_amount'] = $currencies[$currency_code]['minimum'];
+    $form['payment_donation_amount']['#minimum_amount'] = $currencies[$currency_code]['minimum'];
   }
   if (isset($currencies[$currency_code]['maximum'])) {
-    $form['amount']['#maximum_amount'] = $currencies[$currency_code]['maximum'];
+    $form['payment_donation_amount']['#maximum_amount'] = $currencies[$currency_code]['maximum'];
   }
 
   $payment = new Payment(array(
@@ -136,7 +153,10 @@ function payment_donation_form(array $form, array &$form_state) {
   unset($form_info['elements']['payment_status']);
   $form = array_merge($form, $form_info['elements']);
 
-  $form['pay'] = array(
+  $form['actions'] = array(
+    '#type' => 'actions',
+  );
+  $form['actions']['payment_donation_pay'] = array(
     '#value' => t('Pay'),
     '#type' => 'submit',
     '#submit' => array_merge(array('payment_donation_form_submit'), $form_info['submit']),