diff --git a/mod/forum/deprecatedlib.php b/mod/forum/deprecatedlib.php
index 29f2dc35be6..bb5f3d5df96 100644
--- a/mod/forum/deprecatedlib.php
+++ b/mod/forum/deprecatedlib.php
@@ -1690,3 +1690,71 @@ function forum_get_user_grades($forum, $userid = 0) {
     $rm = new rating_manager();
     return $rm->get_user_grades($ratingoptions);
 }
+
+/**
+ * Obtains the automatic completion state for this forum based on any conditions
+ * in forum settings.
+ *
+ * @deprecated since Moodle 3.11
+ * @todo MDL-71196 Final deprecation in Moodle 4.3
+ * @see \mod_forum\completion\custom_completion
+ * @global object
+ * @global object
+ * @param object $course Course
+ * @param object $cm Course-module
+ * @param int $userid User ID
+ * @param bool $type Type of comparison (or/and; can be used as return value if no conditions)
+ * @return bool True if completed, false if not. (If no conditions, then return
+ *   value depends on comparison type)
+ */
+function forum_get_completion_state($course, $cm, $userid, $type) {
+    global $DB;
+
+    // No need to call debugging here. Deprecation debugging notice already being called in \completion_info::internal_get_state().
+
+    // Get forum details.
+    if (!($forum = $DB->get_record('forum', array('id' => $cm->instance)))) {
+        throw new Exception("Can't find forum {$cm->instance}");
+    }
+
+    $result = $type; // Default return value.
+
+    $postcountparams = array('userid' => $userid, 'forumid' => $forum->id);
+    $postcountsql = "
+SELECT
+    COUNT(1)
+FROM
+    {forum_posts} fp
+    INNER JOIN {forum_discussions} fd ON fp.discussion=fd.id
+WHERE
+    fp.userid=:userid AND fd.forum=:forumid";
+
+    if ($forum->completiondiscussions) {
+        $value = $forum->completiondiscussions <=
+            $DB->count_records('forum_discussions', array('forum' => $forum->id, 'userid' => $userid));
+        if ($type == COMPLETION_AND) {
+            $result = $result && $value;
+        } else {
+            $result = $result || $value;
+        }
+    }
+    if ($forum->completionreplies) {
+        $value = $forum->completionreplies <=
+            $DB->get_field_sql($postcountsql . ' AND fp.parent<>0', $postcountparams);
+        if ($type == COMPLETION_AND) {
+            $result = $result && $value;
+        } else {
+            $result = $result || $value;
+        }
+    }
+    if ($forum->completionposts) {
+        $value = $forum->completionposts <= $DB->get_field_sql($postcountsql, $postcountparams);
+        if ($type == COMPLETION_AND) {
+            $result = $result && $value;
+        } else {
+            $result = $result || $value;
+        }
+    }
+
+    return $result;
+}
diff --git a/mod/forum/lib.php b/mod/forum/lib.php
index c619c5a4e4d..d0e09c240f7 100644
--- a/mod/forum/lib.php
+++ b/mod/forum/lib.php
@@ -373,69 +373,6 @@ function forum_supports($feature) {
     }
 }
 
-/**
- * Obtains the automatic completion state for this forum based on any conditions
- * in forum settings.
- *
- * @global object
- * @global object
- * @param object $course Course
- * @param object $cm Course-module
- * @param int $userid User ID
- * @param bool $type Type of comparison (or/and; can be used as return value if no conditions)
- * @return bool True if completed, false if not. (If no conditions, then return
- *   value depends on comparison type)
- */
-function forum_get_completion_state($course,$cm,$userid,$type) {
-    global $CFG,$DB;
-
-    // Get forum details
-    if (!($forum=$DB->get_record('forum',array('id'=>$cm->instance)))) {
-        throw new Exception("Can't find forum {$cm->instance}");
-    }
-
-    $result=$type; // Default return value
-
-    $postcountparams=array('userid'=>$userid,'forumid'=>$forum->id);
-    $postcountsql="
-SELECT
-    COUNT(1)
-FROM
-    {forum_posts} fp
-    INNER JOIN {forum_discussions} fd ON fp.discussion=fd.id
-WHERE
-    fp.userid=:userid AND fd.forum=:forumid";
-
-    if ($forum->completiondiscussions) {
-        $value = $forum->completiondiscussions <=
-                 $DB->count_records('forum_discussions',array('forum'=>$forum->id,'userid'=>$userid));
-        if ($type == COMPLETION_AND) {
-            $result = $result && $value;
-        } else {
-            $result = $result || $value;
-        }
-    }
-    if ($forum->completionreplies) {
-        $value = $forum->completionreplies <=
-                 $DB->get_field_sql( $postcountsql.' AND fp.parent<>0',$postcountparams);
-        if ($type==COMPLETION_AND) {
-            $result = $result && $value;
-        } else {
-            $result = $result || $value;
-        }
-    }
-    if ($forum->completionposts) {
-        $value = $forum->completionposts <= $DB->get_field_sql($postcountsql,$postcountparams);
-        if ($type == COMPLETION_AND) {
-            $result = $result && $value;
-        } else {
-            $result = $result || $value;
-        }
-    }
-
-    return $result;
-}
-
 /**
  * Create a message-id string to use in the custom headers of forum notification emails
  *