--- a/lib/malloc.c
+++ b/lib/malloc.c
@@ -1,9 +1,9 @@
      #include <config.h>
      #undef malloc
      
-     #include <sys/types.h>
+     #include <stdlib.h>
      
-     void *malloc ();
+     #include <sys/types.h>
      
      /* Allocate an N-byte block of memory from the heap.
         If N is zero, allocate a 1-byte block.  */
--- a/src/flexdef.h
+++ b/src/flexdef.h
@@ -38,6 +38,14 @@
 #ifdef HAVE_CONFIG_H
 #include <config.h>
 #endif
+
+#include <stddef.h>
+#ifdef malloc
+void *malloc(size_t);
+#endif
+#ifdef realloc
+void *realloc(void *, size_t);
+#endif
 
 #include <stdio.h>
 #include <stdlib.h>
@@ -76,6 +84,8 @@
 /* Required: strcasecmp() in <strings.h> */
 #include <strings.h>
 #include "flexint.h"
+
+#define flex_isascii(c) (((unsigned int) (c)) <= 0x7f)
 
 /* We use gettext. So, when we write strings which should be translated, we mark them with _() */
 #ifdef ENABLE_NLS
@@ -1078,7 +1088,7 @@
 /* ctype functions forced to return boolean */
 #define b_isalnum(c) (isalnum(c)?true:false)
 #define b_isalpha(c) (isalpha(c)?true:false)
-#define b_isascii(c) (isascii(c)?true:false)
+#define b_isascii(c) (flex_isascii(c)?true:false)
 #define b_isblank(c) (isblank(c)?true:false)
 #define b_iscntrl(c) (iscntrl(c)?true:false)
 #define b_isdigit(c) (isdigit(c)?true:false)
--- a/src/misc.c
+++ b/src/misc.c
@@ -163,7 +163,7 @@
 int all_lower (char *str)
 {
 	while (*str) {
-		if (!isascii ((unsigned char) * str) || !islower ((unsigned char) * str))
+		if (!flex_isascii ((unsigned char) * str) || !islower ((unsigned char) * str))
 			return 0;
 		++str;
 	}
@@ -177,7 +177,7 @@
 int all_upper (char *str)
 {
 	while (*str) {
-		if (!isascii ((unsigned char) * str) || !isupper ((unsigned char) * str))
+		if (!flex_isascii ((unsigned char) * str) || !isupper ((unsigned char) * str))
 			return 0;
 		++str;
 	}
@@ -217,7 +217,7 @@
 
 unsigned char clower (int c)
 {
-	return (unsigned char) ((isascii (c) && isupper (c)) ? tolower (c) : c);
+	return (unsigned char) ((flex_isascii (c) && isupper (c)) ? tolower (c) : c);
 }
 
 
--- a/src/yylex.c
+++ b/src/yylex.c
@@ -151,7 +151,7 @@
 				break;
 
 			default:
-				if (!isascii (yylval) || !isprint (yylval)) {
+				if (!flex_isascii (yylval) || !isprint (yylval)) {
 					if(trace_hex)
 						fprintf (stderr, "\\x%02x", (unsigned int) yylval);
 					else
--- a/src/parse.y
+++ b/src/parse.y
@@ -88,7 +88,7 @@
 	do{ \
 	int c; \
 	for ( c = 0; c < csize; ++c ) \
-		if ( isascii(c) && func(c) ) \
+		if ( flex_isascii(c) && func(c) ) \
 			ccladd( currccl, c ); \
 	}while(0)
 
--- a/src/parse.c
+++ b/src/parse.c
@@ -120,7 +120,7 @@
 	do{ \
 	int c; \
 	for ( c = 0; c < csize; ++c ) \
-		if ( isascii(c) && func(c) ) \
+		if ( flex_isascii(c) && func(c) ) \
 			ccladd( currccl, c ); \
 	}while(0)