diff --git a/include/mes/lib.h b/include/mes/lib.h
index 6b66107b..9ce38f2f 100644
--- a/include/mes/lib.h
+++ b/include/mes/lib.h
@@ -1,6 +1,6 @@
 /* -*-comment-start: "//";comment-end:""-*-
  * GNU Mes --- Maxwell Equations of Software
- * Copyright © 2016,2017,2018,2019 Jan (janneke) Nieuwenhuizen <janneke@gnu.org>
+ * Copyright © 2016,2017,2018,2019,2020 Jan (janneke) Nieuwenhuizen <janneke@gnu.org>
  *
  * This file is part of GNU Mes.
  *
@@ -34,7 +34,7 @@ char *dtoab (double number, int base, int signed_p);
 char *itoa (int number);
 char *ltoa (long number);
 char *ltoab (long x, int base);
-char *ntoab (long number, int base, int signed_p);
+char *ntoab (long number, unsigned base, int signed_p);
 char *ultoa (unsigned long number);
 char *utoa (unsigned number);
 int eputc (int c);
diff --git a/lib/mes/ntoab.c b/lib/mes/ntoab.c
index 45563057..f2f0e89d 100644
--- a/lib/mes/ntoab.c
+++ b/lib/mes/ntoab.c
@@ -1,6 +1,6 @@
 /* -*-comment-start: "//";comment-end:""-*-
  * GNU Mes --- Maxwell Equations of Software
- * Copyright © 2016,2017,2018,2019 Jan (janneke) Nieuwenhuizen <janneke@gnu.org>
+ * Copyright © 2016,2017,2018,2019,2020 Jan (janneke) Nieuwenhuizen <janneke@gnu.org>
  *
  * This file is part of GNU Mes.
  *
@@ -26,7 +26,7 @@
 #define XSTR(s) STR(s)
 
 char *
-ntoab (long x, int base, int signed_p)
+ntoab (long x, unsigned base, int signed_p)
 {
   static char itoa_buf[20];
   char *p = itoa_buf + 11;