diff --git a/src/ContactEmailerServiceProvider.php b/src/ContactEmailerServiceProvider.php
index e0fd82b..ade219e 100644
--- a/src/ContactEmailerServiceProvider.php
+++ b/src/ContactEmailerServiceProvider.php
@@ -9,6 +9,7 @@ use Drupal\Core\Render\Renderer;
 use Drupal\Component\Render\FormattableMarkup;
 use Egulias\EmailValidator\EmailValidator;
 use Drupal\Core\Entity\EntityTypeManagerInterface;
+use Drupal\Core\Mail\MailFormatHelper;
 
 /**
  * Class ContactEmailerServiceProvider.
@@ -133,7 +134,7 @@ class ContactEmailerServiceProvider {
         }
 
         // Subject and body.
-        $params['subject'] = $email->subject;
+        $params['subject'] = $this->setSubject($email->subject);
         $params['message'] = $this->setBody($email->body);
 
         // Set to html mail by default.
@@ -268,6 +269,26 @@ class ContactEmailerServiceProvider {
   }
 
   /**
+   * Set the email message subject.
+   *
+   * @var mixed $body
+   *   A string or text format array.
+   *
+   * @return string
+   *   The plain text.
+   */
+  protected function setSubject($subject) {
+    $subject = $this->tokenizeString($subject);
+
+    // Convert any html to plain text.
+    $subject = MailFormatHelper::htmlToText($subject);
+
+    // Remove any line breaks as the above method assumes new lines allowed.
+    $subject = str_replace("\n", '', $subject);
+    return $subject;
+  }
+
+  /**
    * Set the email message body.
    *
    * @var mixed $body
@@ -288,7 +309,7 @@ class ContactEmailerServiceProvider {
 
       // No text format, plain text.
       $body = [
-        '#plain_text' => $this->tokenizeBody($body),
+        '#plain_text' => $this->tokenizeString($body),
       ];
     }
     else {
@@ -297,7 +318,7 @@ class ContactEmailerServiceProvider {
       $body = [
         '#type' => 'processed_text',
         '#format' => $body['format'],
-        '#text' => $this->tokenizeBody($body['value']),
+        '#text' => $this->tokenizeString($body['value']),
       ];
     }
 
@@ -311,14 +332,14 @@ class ContactEmailerServiceProvider {
   /**
    * Apply tokens to body value.
    *
-   * @param string $body
-   *   The body string value.
+   * @param string $string
+   *   The string value such as the subject or body.
    *
    * @return string
-   *   The tokenized body.
+   *   The tokenized value.
    */
-  protected function tokenizeBody($body) {
-    return $this->token->replace($body, [
+  protected function tokenizeString($string) {
+    return $this->token->replace($string, [
       'contact_message' => $this->contactMessage,
     ]);
   }
diff --git a/src/Form/ContactEmailSettingsForm.php b/src/Form/ContactEmailSettingsForm.php
index 7d82e40..6d96d1b 100644
--- a/src/Form/ContactEmailSettingsForm.php
+++ b/src/Form/ContactEmailSettingsForm.php
@@ -76,10 +76,12 @@ class ContactEmailSettingsForm extends FormBase {
       $form['subject'] = [
         '#type' => 'textfield',
         '#title' => $this->t('Subject'),
-        '#description' => $this->t('The subject of the email.'),
         '#maxlength' => 255,
         '#required' => TRUE,
         '#size' => 64,
+        '#description' => $this->t('The subject of the email. To add a variable, click within the above field and then click the "Browse available tokens" link below. You will find the fields of your forms within Contact Message. Note that tokens that produce html markup are not supported for an email subject.'),
+        '#element_validate' => ['token_element_validate'],
+        '#token_types' => ['contact_message'],
         '#default_value' => ($email ? $email['subject'] : ''),
       ];