Backport: #1889 - fixup \xhh specs.
diff --git a/Doc/ref/ref2.tex b/Doc/ref/ref2.tex
index bad4609..800031e 100644
--- a/Doc/ref/ref2.tex
+++ b/Doc/ref/ref2.tex
@@ -485,7 +485,7 @@
 \item[(3)]
   As in Standard C, up to three octal digits are accepted.
 \item[(4)]
-  Unlike in Standard C, at most two hex digits are accepted.
+  Unlike in Standard C, exactly two hex digits are required.
 \item[(5)]
   In a string literal, hexadecimal and octal escapes denote the
   byte with the given value; it is not necessary that the byte