diff --git a/bin/Release/README.txt b/bin/Release/README.txt
index e2c3854..922ab5b 100644
--- a/bin/Release/README.txt
+++ b/bin/Release/README.txt
@@ -1,3 +1,9 @@
+version 2.2
+--------------
+added --wincompat option to win_flex (this option changes <unistd.h> unix include with <io.h> windows analog
+  also isatty/fileno functions changed to _isatty/_fileno)
+fixed two "'<' : signed/unsigned mismatch" warnings in win_flex generated file
+
 version 2.1
 --------------
 fixed crash when execute win_bison.exe under WindowsXP (argv[0] don't have full application path)
diff --git a/bin/Release/UNISTD_ERROR.readme b/bin/Release/UNISTD_ERROR.readme
new file mode 100644
index 0000000..3b14a38
--- /dev/null
+++ b/bin/Release/UNISTD_ERROR.readme
@@ -0,0 +1,4 @@
+In case compile errors like "cannot include <unistd.h>" in win_flex generated file try add --wincompat invoke option.
+This new option changes <unistd.h> unix header with windows analog <io.h> and replaces isatty/fileno functions to 
+"safe" windows analogs _isatty/_fileno as well. If you have compile issues with it afterwards please open ticket
+at http://sourceforge.net/p/winflexbison/tickets .
\ No newline at end of file
diff --git a/bin/Release/win_bison.exe b/bin/Release/win_bison.exe
index fa0bf03..2fcb6bd 100644
Binary files a/bin/Release/win_bison.exe and b/bin/Release/win_bison.exe differ
diff --git a/bin/Release/win_flex.exe b/bin/Release/win_flex.exe
index 6b23b49..dc87f20 100644
Binary files a/bin/Release/win_flex.exe and b/bin/Release/win_flex.exe differ
diff --git a/flex/src/gen.c b/flex/src/gen.c
index 5a5daef..8d24a86 100644
--- a/flex/src/gen.c
+++ b/flex/src/gen.c
@@ -1972,7 +1972,7 @@ void make_tables ()
 		("if ( yy_act != YY_END_OF_BUFFER && yy_rule_can_match_eol[yy_act] )");
 	indent_up ();
 	indent_puts ("{");
-	indent_puts ("int yyl;");
+	indent_puts ("yy_size_t yyl;");
 	do_indent ();
 	out_str ("for ( yyl = %s; yyl < yyleng; ++yyl )\n",
 		 yymore_used ? (yytext_is_array ? "YY_G(yy_prev_more_offset)" :
diff --git a/flex/src/main.c b/flex/src/main.c
index dde0746..b0fe98d 100644
--- a/flex/src/main.c
+++ b/flex/src/main.c
@@ -1026,6 +1026,10 @@ void flexinit (argc, argv)
             buf_m4_define( &m4defs_buf, "M4_YY_NO_UNISTD_H",0);
 			break;
 
+		case OPT_WIN_COMPAT:
+            buf_m4_define( &m4defs_buf, "M4_YY_WIN_COMPAT",0);
+			break;
+
 		case OPT_TABLES_FILE:
 			tablesext = true;
 			tablesfilename = arg;
@@ -1711,6 +1715,7 @@ void usage ()
           "       --noansi-definitions old-style function definitions\n"
           "       --noansi-prototypes  empty parameter list in prototypes\n"
 		  "       --nounistd          do not include <unistd.h>\n"
+		  "       --wincompat         windows compatibility (uses <io.h> instead of <unistd.h> and _isatty, _fileno functions)\n"
 		  "       --noFUNCTION        do not generate a particular FUNCTION\n"
 		  "\n" "Miscellaneous:\n"
 		  "  -c                      do-nothing POSIX option\n"
diff --git a/flex/src/options.c b/flex/src/options.c
index c673173..21ab0c2 100644
--- a/flex/src/options.c
+++ b/flex/src/options.c
@@ -193,10 +193,12 @@ optspec_t flexopts[] = {
 	,			/* Flex should run in trace mode. */
 	{"--tables-file[=FILE]", OPT_TABLES_FILE, 0}
 	,			/* Save tables to FILE */
-        {"--tables-verify", OPT_TABLES_VERIFY, 0}
-        ,                       /* Tables integrity check */
+    {"--tables-verify", OPT_TABLES_VERIFY, 0}
+    ,                       /* Tables integrity check */
 	{"--nounistd", OPT_NO_UNISTD_H, 0}
 	,			/* Do not include unistd.h */
+	{"--wincompat", OPT_WIN_COMPAT, 0}
+	,			/* windows compatibility */
 	{"-v", OPT_VERBOSE, 0}
 	,
 	{"--verbose", OPT_VERBOSE, 0}
diff --git a/flex/src/options.h b/flex/src/options.h
index 1f3925b..174e3c7 100644
--- a/flex/src/options.h
+++ b/flex/src/options.h
@@ -126,7 +126,8 @@ enum flexopt_flag_t {
 	OPT_YYCLASS,
 	OPT_YYLINENO,
 	OPT_YYMORE,
-	OPT_YYWRAP
+	OPT_YYWRAP,
+	OPT_WIN_COMPAT
 };
 
 #endif
diff --git a/flex/src/skel.c b/flex/src/skel.c
index 45a4a11..53a6f8d 100644
--- a/flex/src/skel.c
+++ b/flex/src/skel.c
@@ -831,6 +831,14 @@ const char *skel[] = {
   "",
   "m4_ifdef( [[M4_YY_NO_UNISTD_H]],,",
   "[[",
+  "    m4_ifdef( [[M4_YY_WIN_COMPAT]],",
+  "    [[",
+  "/*windows compatibility case*/",
+  "#include <io.h>",
+  "#define isatty _isatty",
+  "#define fileno _fileno",
+  "    ]],",
+  "    [[",
   "#ifndef YY_NO_UNISTD_H",
   "/* Special case for \"unistd.h\", since it is non-ANSI. We include it way",
   " * down here because we want the user's section 1 to have been scanned first.",
@@ -843,6 +851,7 @@ const char *skel[] = {
   "#include <unistd.h>",
   "%endif",
   "#endif",
+  "    ]])",
   "]])",
   "",
   "m4_ifdef( [[M4_EXTRA_TYPE_DEFS]],",
@@ -2571,7 +2580,7 @@ const char *skel[] = {
   "	YY_BUFFER_STATE b;",
   "	char *buf;",
   "	yy_size_t n;",
-  "	int i;",
+  "	yy_size_t i;",
   "    m4_dnl M4_YY_DECL_GUTS_VAR();",
   "",
   "	/* Get memory for full buffer, including space for trailing EOB's. */",