Index: cm1/index.php
===================================================================
--- cm1/index.php	(revision 28850)
+++ cm1/index.php	(working copy)
@@ -1731,8 +1731,13 @@
 			$optDat = array_reverse($optDat);
 		}
 
-			// Add options for "samelevel" elements:
-		$sameLevelElements = $this->markupObj->elParentLevel[$lastEl['parent']];
+			/**
+			 * Add options for "samelevel" elements -
+			 * If element has an id the "parent" is empty, therefore we need two steps to get the elements (see #11842)
+			 */
+		$parentElement = strlen($lastEl['parent']) ? $lastEl['parent'] : $this->markupObj->elParentLevel[$lastEl['parent']][0];
+		$sameLevelElements =  $this->markupObj->elParentLevel[$parentElement];
+
 		if (is_array($sameLevelElements))	{
 			$startFound=0;
 			foreach($sameLevelElements as $rEl) 	{