Index: docs/LangRef.rst
===================================================================
--- docs/LangRef.rst
+++ docs/LangRef.rst
@@ -7595,7 +7595,8 @@
 
 The result is a scalar of the same type as the element type of ``val``.
 Its value is the value at position ``idx`` of ``val``. If ``idx``
-exceeds the length of ``val``, the results are undefined.
+exceeds the length of ``val``, the result is a
+:ref:`poison value <poisonvalues>`.
 
 Example:
 """"""""
@@ -7636,8 +7637,8 @@
 
 The result is a vector of the same type as ``val``. Its element values
 are those of ``val`` except at position ``idx``, where it gets the value
-``elt``. If ``idx`` exceeds the length of ``val``, the results are
-undefined.
+``elt``. If ``idx`` exceeds the length of ``val``, the result
+is a :ref:`poison value <poisonvalues>`.
 
 Example:
 """"""""