diff --git a/clang/docs/UndefinedBehaviorSanitizer.rst b/clang/docs/UndefinedBehaviorSanitizer.rst
--- a/clang/docs/UndefinedBehaviorSanitizer.rst
+++ b/clang/docs/UndefinedBehaviorSanitizer.rst
@@ -157,7 +157,8 @@
      ``-fsanitize=shift-exponent`` to check only left-hand side or
      right-hand side of shift operation, respectively.
   -  ``-fsanitize=unsigned-shift-base``: check that an unsigned left-hand side of
-     a left shift operation doesn't overflow.
+     a left shift operation doesn't overflow. Issues caught by this sanitizer are 
+     not undefined behavior, but are often unintentional.
   -  ``-fsanitize=signed-integer-overflow``: Signed integer overflow, where the
      result of a signed integer computation cannot be represented in its type.
      This includes all the checks covered by ``-ftrapv``, as well as checks for