diff --git a/api/v3/TwingleDonation/Submit.php b/api/v3/TwingleDonation/Submit.php
index d307424..9ebbfb6 100644
--- a/api/v3/TwingleDonation/Submit.php
+++ b/api/v3/TwingleDonation/Submit.php
@@ -533,6 +533,7 @@ function civicrm_api3_twingle_donation_Submit($params) {
     if (
       (bool) $profile->getAttribute('newsletter_double_opt_in')
       && isset($params['newsletter'])
+      && 1 == $params['newsletter']
       && is_array($groups = $profile->getAttribute('newsletter_groups'))
     ) {
       $group_memberships = array_column(
@@ -573,6 +574,7 @@ function civicrm_api3_twingle_donation_Submit($params) {
     }
     elseif (
       isset($params['newsletter'])
+      && 1 == $params['newsletter']
       && is_array($groups = $profile->getAttribute('newsletter_groups'))
     ) {
       foreach ($groups as $group_id) {
@@ -592,6 +594,7 @@ function civicrm_api3_twingle_donation_Submit($params) {
     // If requested, add contact to postinfo groups defined in the profile.
     if (
       isset($params['postinfo'])
+      && 1 == $params['postinfo']
       && is_array($groups = $profile->getAttribute('postinfo_groups'))
     ) {
       foreach ($groups as $group_id) {
@@ -609,6 +612,7 @@ function civicrm_api3_twingle_donation_Submit($params) {
     // (see issue #83)
     if (
       isset($params['donation_receipt'])
+      && 1 == $params['donation_receipt']
       && is_array($groups = $profile->getAttribute('donation_receipt_groups'))
     ) {
       foreach ($groups as $group_id) {