--- a/lib/minitasn1/decoding.c
+++ b/lib/minitasn1/decoding.c
@@ -32,7 +32,6 @@
 #include <element.h>
 #include <limits.h>
 #include <intprops.h>
-#include "c-ctype.h"
 
 #ifdef DEBUG
 # define warn() fprintf(stderr, "%s: %d\n", __func__, __LINE__)
@@ -355,7 +355,7 @@
      p = &der[len_len];
      for (i = 0; i < (unsigned) (str_len - 1); i++)
	{
-	  if (c_isdigit (p[i]) == 0)
+	  if (isdigit (p[i]) == 0)
	    {
	      if (type == ASN1_ETYPE_GENERALIZED_TIME)
		{
--- a/lib/minitasn1/element.c
+++ b/lib/minitasn1/element.c
@@ -30,7 +30,6 @@
 #include "parser_aux.h"
 #include <gstr.h>
 #include "structure.h"
-#include "c-ctype.h"
 #include "element.h"
 
 void
@@ -380,7 +379,7 @@
     case ASN1_ETYPE_ENUMERATED:
       if (len == 0)
 	{
-	  if ((c_isdigit (value[0])) || (value[0] == '-'))
+	  if ((isdigit (value[0])) || (value[0] == '-'))
 	    {
 	      value_temp = malloc (SIZEOF_UNSIGNED_LONG_INT);
 	      if (value_temp == NULL)
@@ -453,7 +452,7 @@
 	  p = node->down;
 	  while (type_field (p->type) != ASN1_ETYPE_DEFAULT)
 	    p = p->right;
-	  if ((c_isdigit (p->value[0])) || (p->value[0] == '-'))
+	  if ((isdigit (p->value[0])) || (p->value[0] == '-'))
 	    {
 	      default_temp = malloc (SIZEOF_UNSIGNED_LONG_INT);
 	      if (default_temp == NULL)
@@ -519,7 +518,7 @@
       break;
     case ASN1_ETYPE_OBJECT_ID:
       for (i = 0; i < _asn1_strlen (value); i++)
-	if ((!c_isdigit (value[i])) && (value[i] != '.') && (value[i] != '+'))
+	if ((!isdigit (value[i])) && (value[i] != '.') && (value[i] != '+'))
 	  return ASN1_VALUE_NOT_VALID;
       if (node->type & CONST_DEFAULT)
 	{
@@ -540,7 +539,7 @@
 	if (len < 11)
 	  return ASN1_VALUE_NOT_VALID;
 	for (k = 0; k < 10; k++)
-	  if (!c_isdigit (value[k]))
+	  if (!isdigit (value[k]))
 	    return ASN1_VALUE_NOT_VALID;
 	switch (len)
 	  {
@@ -549,7 +548,7 @@
 	      return ASN1_VALUE_NOT_VALID;
 	    break;
 	  case 13:
-	    if ((!c_isdigit (value[10])) || (!c_isdigit (value[11])) ||
+	    if ((!isdigit (value[10])) || (!isdigit (value[11])) ||
 		(value[12] != 'Z'))
 	      return ASN1_VALUE_NOT_VALID;
 	    break;
@@ -557,16 +556,16 @@
 	    if ((value[10] != '+') && (value[10] != '-'))
 	      return ASN1_VALUE_NOT_VALID;
 	    for (k = 11; k < 15; k++)
-	      if (!c_isdigit (value[k]))
+	      if (!isdigit (value[k]))
 		return ASN1_VALUE_NOT_VALID;
 	    break;
 	  case 17:
-	    if ((!c_isdigit (value[10])) || (!c_isdigit (value[11])))
+	    if ((!isdigit (value[10])) || (!isdigit (value[11])))
 	      return ASN1_VALUE_NOT_VALID;
 	    if ((value[12] != '+') && (value[12] != '-'))
 	      return ASN1_VALUE_NOT_VALID;
 	    for (k = 13; k < 17; k++)
-	      if (!c_isdigit (value[k]))
+	      if (!isdigit (value[k]))
 		return ASN1_VALUE_NOT_VALID;
 	    break;
 	  default:
@@ -890,7 +889,7 @@
 	  p = node->down;
 	  while (type_field (p->type) != ASN1_ETYPE_DEFAULT)
 	    p = p->right;
-	  if ((c_isdigit (p->value[0])) || (p->value[0] == '-')
+	  if ((isdigit (p->value[0])) || (p->value[0] == '-')
 	      || (p->value[0] == '+'))
 	    {
 	      result = _asn1_convert_integer

--- a/lib/minitasn1/int.h
+++ b/lib/minitasn1/int.h
@@ -29,6 +29,7 @@
 # include <string.h>
 # include <stdlib.h>
 # include <stdio.h>
+# include <ctype.h>
 # include <stdint.h>

 # ifdef HAVE_SYS_TYPES_H
--- a/lib/minitasn1/parser_aux.c
+++ b/lib/minitasn1/parser_aux.c
@@ -26,7 +26,6 @@
 #include "gstr.h"
 #include "structure.h"
 #include "element.h"
-#include "c-ctype.h"
 
 char _asn1_identifierMissing[ASN1_MAX_NAME_SIZE + 1];	/* identifier name not found */
 
@@ -755,7 +754,7 @@
 	      p2 = p->down;
 	      if (p2 && (type_field (p2->type) == ASN1_ETYPE_CONSTANT))
 		{
-		  if (p2->value && !c_isdigit (p2->value[0]))
+		  if (p2->value && !isdigit (p2->value[0]))
 		    {
 		      _asn1_str_cpy (name2, sizeof (name2), name_root);
 		      _asn1_str_cat (name2, sizeof (name2), ".");
@@ -1067,7 +1066,7 @@
 	  p2 = p->down;
 	  if (p2 && (type_field (p2->type) == ASN1_ETYPE_CONSTANT))
 	    {
-	      if (p2->value && !c_isdigit (p2->value[0]))
+	      if (p2->value && !isdigit (p2->value[0]))
 		{
 		  _asn1_str_cpy (name2, sizeof (name2), node->name);
 		  _asn1_str_cat (name2, sizeof (name2), ".");