diff --git a/configure.in b/configure.in
index 7c2a4a5..ce59133 100644
--- a/configure.in
+++ b/configure.in
@@ -62,6 +62,8 @@ AC_PROG_RANLIB
 dnl Avoid unused static function warnings
 CFLAGS="-Wall $CFLAGS"
 if test "x$GCC" = "xyes"; then
+	# this may produce a harmless warning with older GCC's:
+	#   unrecognized option '-Wno-unused-function'
 	CFLAGS="$CFLAGS -Wno-unused-function"
 fi
 export CFLAGS