diff --git a/docs/ReleaseNotes.rst b/docs/ReleaseNotes.rst
index 6f4644c01cd88167f94d8ee32029bc43e9658f62..b65c3bf9887e7f6ee92741284e4d426a4f0c239a 100644
--- a/docs/ReleaseNotes.rst
+++ b/docs/ReleaseNotes.rst
@@ -78,6 +78,11 @@ Improvements to Clang's diagnostics
   when the signed integer is coerced to an unsigned type for the comparison.
   ``-Wsign-compare`` was adjusted not to warn in this case.
 
+- ``-Wnull-pointer-arithmetic`` now warns about performing pointer arithmetic
+  on a null pointer. Such pointer arithmetic has an undefined behavior if the
+  offset is nonzero. It also now warns about arithmetic on a null pointer
+  treated as a cast from integer to pointer (GNU extension).
+
 Non-comprehensive list of changes in this release
 -------------------------------------------------