diff --git a/mod/forum/classes/subscriptions.php b/mod/forum/classes/subscriptions.php
index 8f7aa2fea65..ada9b4d9e96 100644
--- a/mod/forum/classes/subscriptions.php
+++ b/mod/forum/classes/subscriptions.php
@@ -825,4 +825,39 @@ class subscriptions {
         return true;
     }
 
+    /**
+     * Gets the default subscription value for the logged in user.
+     *
+     * @param \stdClass $forum The forum record
+     * @param \context $context The course context
+     * @param \cm_info $cm cm_info
+     * @param int|null $discussionid The discussion we are checking against
+     * @return bool Default subscription
+     * @throws coding_exception
+     */
+    public static function get_user_default_subscription($forum, $context, $cm, $discussionid = null) {
+        global $USER;
+        $manageactivities = has_capability('moodle/course:manageactivities', $context);
+        if (self::subscription_disabled($forum) && !$manageactivities) {
+            // User does not have permission to subscribe to this discussion at all.
+            $discussionsubscribe = false;
+        } else if (self::is_forcesubscribed($forum)) {
+            // User does not have permission to unsubscribe from this discussion at all.
+            $discussionsubscribe = true;
+        } else {
+            if (isset($discussion) && self::is_subscribed($USER->id, $forum, $discussionid, $cm)) {
+                // User is subscribed to the discussion - continue the subscription.
+                $discussionsubscribe = true;
+            } else if (!isset($discussionid) && self::is_subscribed($USER->id, $forum, null, $cm)) {
+                // Starting a new discussion, and the user is subscribed to the forum - subscribe to the discussion.
+                $discussionsubscribe = true;
+            } else {
+                // User is not subscribed to either forum or discussion. Follow user preference.
+                $discussionsubscribe = $USER->autosubscribe ? $USER->autosubscribe : false;
+            }
+        }
+
+        return $discussionsubscribe;
+    }
+
 }
diff --git a/mod/forum/externallib.php b/mod/forum/externallib.php
index a92d3bd5b05..6a0aaa0b19b 100644
--- a/mod/forum/externallib.php
+++ b/mod/forum/externallib.php
@@ -823,9 +823,14 @@ class mod_forum_external extends external_api {
         $context = context_module::instance($cm->id);
         self::validate_context($context);
 
+        $coursecontext = \context_course::instance($course->id);
+        $discussionsubscribe = \mod_forum\subscriptions::get_user_default_subscription($forum, $coursecontext,
+            $cm, null);
+
         // Validate options.
         $options = array(
-            'discussionsubscribe' => true,
+            'discussionsubscribe' => $discussionsubscribe,
+            'private'             => false,
             'inlineattachmentsid' => 0,
             'attachmentsid' => null
         );
@@ -896,9 +901,11 @@ class mod_forum_external extends external_api {
                 $completion->update_state($cm, COMPLETION_COMPLETE);
             }
 
-            $settings = new stdClass();
-            $settings->discussionsubscribe = $options['discussionsubscribe'];
-            forum_post_subscription($settings, $forum, $discussion);
+            if ($options['discussionsubscribe']) {
+                $settings = new stdClass();
+                $settings->discussionsubscribe = $options['discussionsubscribe'];
+                forum_post_subscription($settings, $forum, $discussion);
+            }
         } else {
             throw new moodle_exception('couldnotadd', 'forum');
         }