Index: src/includes/topics/functions.php
===================================================================
--- src/includes/topics/functions.php
+++ src/includes/topics/functions.php
@@ -249,7 +249,7 @@
 
 	/** Topic Duplicate *******************************************************/
 
-	if ( ! bbp_check_for_duplicate( array( 'post_type' => bbp_get_topic_post_type(), 'post_author' => $topic_author, 'post_content' => $topic_content, 'anonymous_data' => $anonymous_data ) ) ) {
+	if ( ! bbp_check_for_duplicate( array( 'post_type' => bbp_get_topic_post_type(), 'post_author' => $topic_author, 'post_content' => $topic_content, 'post_parent' => $forum_id, 'anonymous_data' => $anonymous_data ) ) ) {
 		bbp_add_error( 'bbp_topic_duplicate', __( '<strong>Error</strong>: Duplicate topic detected; it looks as though you&#8217;ve already said that.', 'bbpress' ) );
 	}