https://support.ntp.org/bugs/show_bug.cgi?id=769
http://bugs.gentoo.org/254030

--- ntp/util/tickadj.c
+++ ntp/util/tickadj.c
@@ -21,7 +21,8 @@
 # include <unistd.h>
 #endif /* HAVE_UNISTD_H */
 
-#ifdef HAVE___ADJTIMEX		/* Linux */
+/* proper handling here has been moved to upstream ntp bugzilla */
+#ifdef linux
 
 #include <sys/timex.h>
 struct timex txc;
@@ -91,7 +92,7 @@
 	}
 
 	if (!errflg) {
-		if (__adjtimex(&txc) < 0)
+		if (adjtimex(&txc) < 0)
 			perror("adjtimex");
 		else if (!quiet)
 			printf("tick     = %ld\ntick_adj = %d\n",
@@ -146,7 +147,7 @@
 #endif
 	}
     
-	if (__adjtimex(&txc) < 0)
+	if (adjtimex(&txc) < 0)
 	{
 		perror("adjtimex");
 	}