diff --git a/core/modules/comment/comment.entity.inc b/core/modules/comment/comment.entity.inc
index 796bbe8..140396a 100644
--- a/core/modules/comment/comment.entity.inc
+++ b/core/modules/comment/comment.entity.inc
@@ -141,8 +141,11 @@ class CommentStorageController extends EntityDatabaseStorageController {
         $max = db_query('SELECT MAX(thread) FROM {comment} WHERE nid = :nid', array(':nid' => $comment->nid))->fetchField();
         // Strip the "/" from the end of the thread.
         $max = rtrim($max, '/');
+        // We need to get the value at the correct depth.
+        $parts = explode('.', $max);
+        $firstsegment = $parts[0];
         // Finally, build the thread field for this new comment.
-        $thread = comment_increment_alphadecimal($max) . '/';
+        $thread = comment_increment_alphadecimal($firstsegment) .'/';
       }
       else {
         // This is a comment with a parent comment, so increase the part of
diff --git a/core/modules/comment/comment.test b/core/modules/comment/comment.test
index 74f735d..7b2499a 100644
--- a/core/modules/comment/comment.test
+++ b/core/modules/comment/comment.test
@@ -2117,3 +2117,98 @@ class CommentFieldsTest extends CommentHelperCase {
     $this->drupalPost('node/' . $this->node->nid, $edit, t('Save'));
   }
 }
+
+/**
+ * Tests comment threading.
+ */
+class CommentThreadingTestCase extends CommentHelperCase {
+  public static function getInfo() {
+    return array(
+      'name' => 'Comment Threading',
+      'description' => 'Test to make sure the comment number increments properly.',
+      'group' => 'Comment',
+    );
+  }
+
+  /**
+   * Tests the comment threading.
+   */
+  function testCommentThreading() {
+    $langcode = LANGUAGE_NONE;
+    // Set comments to have a subject with preview disabled.
+    $this->drupalLogin($this->admin_user);
+    $this->setCommentPreview(DRUPAL_DISABLED);
+    $this->setCommentForm(TRUE);
+    $this->setCommentSubject(TRUE);
+    $this->setCommentSettings('comment_default_mode', COMMENT_MODE_THREADED, t('Comment paging changed.'));
+    $this->drupalLogout();
+
+    // Create a node.
+    $this->drupalLogin($this->web_user);
+    $this->node = $this->drupalCreateNode(array('type' => 'article', 'promote' => 1, 'uid' => $this->web_user->uid));
+
+    // Post comment #1.
+    $this->drupalLogin($this->web_user);
+    $subject_text = $this->randomName();
+    $comment_text = $this->randomName();
+    $comment = $this->postComment($this->node, $comment_text, $subject_text, TRUE);
+    $comment_loaded = comment_load($comment->id);
+    $this->assertTrue($this->commentExists($comment), 'Comment #1. Comment found.');
+    $this->assertEqual($comment_loaded->thread, '01/');
+
+    // Reply to comment #1 creating comment #2.
+    $this->drupalLogin($this->web_user);
+    $this->drupalGet('comment/reply/' . $this->node->nid . '/' . $comment->id);
+    $reply = $this->postComment(NULL, $this->randomName(), '', TRUE);
+    $reply_loaded = comment_load($reply->id);
+    $this->assertTrue($this->commentExists($reply, TRUE), 'Comment #2. Reply found.');
+    $this->assertEqual($reply_loaded->thread, '01.00/');
+
+    // Reply to comment #2 creating comment #3.
+    $this->drupalGet('comment/reply/' . $this->node->nid . '/' . $reply->id);
+    $reply = $this->postComment(NULL, $this->randomName(), $this->randomName(), TRUE);
+    $reply_loaded = comment_load($reply->id);
+    $this->assertTrue($this->commentExists($reply, TRUE), 'Comment #3. Second reply found.');
+    $this->assertEqual($reply_loaded->thread, '01.00.00/');
+
+    // Reply to comment #1 creating comment #4.
+    $this->drupalLogin($this->web_user);
+    $this->drupalGet('comment/reply/' . $this->node->nid . '/' . $comment->id);
+    $reply = $this->postComment(NULL, $this->randomName(), '', TRUE);
+    $reply_loaded = comment_load($reply->id);
+    $this->assertTrue($this->commentExists($comment), 'Comment #4. Third reply found.');
+    $this->assertEqual($reply_loaded->thread, '01.01/');
+
+    // Post comment #2 overall comment #5.
+    $this->drupalLogin($this->web_user);
+    $subject_text = $this->randomName();
+    $comment_text = $this->randomName();
+    $comment = $this->postComment($this->node, $comment_text, $subject_text, TRUE);
+    $comment_loaded = comment_load($comment->id);
+    $this->assertTrue($this->commentExists($comment), 'Comment #5. Second comment found.');
+    $this->assertEqual($comment_loaded->thread, '02/');
+
+    // Reply to comment #5 creating comment #6.
+    $this->drupalLogin($this->web_user);
+    $this->drupalGet('comment/reply/' . $this->node->nid . '/' . $comment->id);
+    $reply = $this->postComment(NULL, $this->randomName(), '', TRUE);
+    $reply_loaded = comment_load($reply->id);
+    $this->assertTrue($this->commentExists($reply, TRUE), 'Comment #6. Reply found.');
+    $this->assertEqual($reply_loaded->thread, '02.00/');
+
+    // Reply to comment #6 creating comment #7.
+    $this->drupalGet('comment/reply/' . $this->node->nid . '/' . $reply->id);
+    $reply = $this->postComment(NULL, $this->randomName(), $this->randomName(), TRUE);
+    $reply_loaded = comment_load($reply->id);
+    $this->assertTrue($this->commentExists($reply, TRUE), 'Comment #7. Second reply found.');
+    $this->assertEqual($reply_loaded->thread, '02.00.00/');
+
+    // Reply to comment #5 creating comment #8.
+    $this->drupalLogin($this->web_user);
+    $this->drupalGet('comment/reply/' . $this->node->nid . '/' . $comment->id);
+    $reply = $this->postComment(NULL, $this->randomName(), '', TRUE);
+    $reply_loaded = comment_load($reply->id);
+    $this->assertTrue($this->commentExists($comment), 'Comment #8. Third reply found.');
+    $this->assertEqual($reply_loaded->thread, '02.01/');
+  }
+}