diff --git a/llvm/docs/LangRef.rst b/llvm/docs/LangRef.rst
--- a/llvm/docs/LangRef.rst
+++ b/llvm/docs/LangRef.rst
@@ -9085,12 +9085,10 @@
 to the result. Non-negative elements in the mask represent an index
 into the concatenated pair of input vectors.
 
-If the shuffle mask is undefined, the result vector is undefined. If
+If the shuffle mask is undefined, the result vector is poison. If
 the shuffle mask selects an undefined element from one of the input
 vectors, the resulting element is undefined. An undefined element
-in the mask vector specifies that the resulting element is undefined.
-An undefined element in the mask vector prevents a poisoned vector
-element from propagating.
+in the mask vector specifies that the resulting element is poison.
 
 For scalable vectors, the only valid mask values at present are
 ``zeroinitializer`` and ``undef``, since we cannot write all indices as