diff --git a/source/utilities.tex b/source/utilities.tex
index 0cf351ef54..5a8ff5e6e0 100644
--- a/source/utilities.tex
+++ b/source/utilities.tex
@@ -15535,7 +15535,7 @@
 the optional exponent part shall not appear; and
 \item
 if \tcode{fmt} is \tcode{chars_format::hex},
-the prefix \tcode{"0x"} or \tcode{"0X"} is assumed.
+the prefix \tcode{"0x"} or \tcode{"0X"} shall not appear.
 \begin{example}
 The string \tcode{0x123}
 is parsed to have the value