diff --git a/gas/ChangeLog b/gas/ChangeLog
index bb827aa280..19fb02f7de 100644
--- a/gas/ChangeLog
+++ b/gas/ChangeLog
@@ -1,3 +1,8 @@
+2018-02-20  Thomas Preud'homme  <thomas.preudhomme@arm.com>
+
+	* doc/c-arm.texi (.arch_extension): Mention extensions it accepts are
+	also the same as -march.
+
 2018-02-17  H.J. Lu  <hongjiu.lu@intel.com>
 
 	* NEWS: Mention .nop directive.
diff --git a/gas/doc/c-arm.texi b/gas/doc/c-arm.texi
index ec0f544794..f67696f00f 100644
--- a/gas/doc/c-arm.texi
+++ b/gas/doc/c-arm.texi
@@ -631,7 +631,7 @@ extensions.
 @item .arch_extension @var{name}
 Add or remove an architecture extension to the target architecture.  Valid
 values for @var{name} are the same as those accepted as architectural
-extensions by the @option{-mcpu} commandline option.
+extensions by the @option{-mcpu} and @option{-march} commandline options.
 
 @code{.arch_extension} may be used multiple times to add or remove extensions
 incrementally to the architecture being compiled for.