diff --git a/vlib/benchmark/benchmark.v b/vlib/benchmark/benchmark.v
index e00e1f49a3..ddbcc5ebaf 100644
--- a/vlib/benchmark/benchmark.v
+++ b/vlib/benchmark/benchmark.v
@@ -104,7 +104,7 @@ pub fn (b mut Benchmark) total_duration() i64 {
 fn (b mut Benchmark) tdiff_in_ms(s string, sticks i64, eticks i64) string {
 	if b.verbose {
 		tdiff := (eticks - sticks)
-		return '${tdiff:6d} ms | $s'
+		return '${tdiff:6lld} ms | $s'
 	}
 	return s
 }
diff --git a/vlib/builtin/builtin.v b/vlib/builtin/builtin.v
index f88b8ba236..0becdf91a4 100644
--- a/vlib/builtin/builtin.v
+++ b/vlib/builtin/builtin.v
@@ -6,7 +6,7 @@ module builtin
 
 fn init() {
 	$if windows {	
-		if is_atty(0) {
+		if is_atty(0) > 0 {
 			C._setmode(C._fileno(C.stdin), C._O_U16TEXT)
 		} else {
 			C._setmode(C._fileno(C.stdin), C._O_U8TEXT)		
@@ -195,13 +195,13 @@ fn v_ptr_free(ptr voidptr) {
 	C.free(ptr)
 }
 
-pub fn is_atty(fd int) bool {
+pub fn is_atty(fd int) int {
 	$if windows {
 		mut mode := 0
 		C.GetConsoleMode(C._get_osfhandle(fd), &mode)
-		return mode > 0
+		return mode
 	} $else {
-		return C.isatty(fd) != 0
+		return C.isatty(fd)
 	}
 }
 
diff --git a/vlib/compiler/fn.v b/vlib/compiler/fn.v
index 19d3bfb79b..53f5968308 100644
--- a/vlib/compiler/fn.v
+++ b/vlib/compiler/fn.v
@@ -645,7 +645,11 @@ fn (p mut Parser) async_fn_call(f Fn, method_ph int, receiver_var, receiver_type
 	// Also register the wrapper, so we can use the original function without modifying it
 	fn_name = p.table.fn_gen_name(f)
 	wrapper_name := '${fn_name}_thread_wrapper'
-	wrapper_text := 'void* $wrapper_name($arg_struct_name * arg) {$fn_name( /*f*/$str_args );  }'
+	mut wrapper_type := 'void*'
+	if p.os == .windows {
+		wrapper_type = 'void* __stdcall'
+	}
+	wrapper_text := '$wrapper_type $wrapper_name($arg_struct_name * arg) {$fn_name( /*f*/$str_args );  }'
 	p.cgen.register_thread_fn(wrapper_name, wrapper_text, arg_struct)
 	// Create thread object
 	tmp_nr := p.get_tmp_counter()
diff --git a/vlib/os/os.v b/vlib/os/os.v
index 26538440c1..93f13d2adc 100644
--- a/vlib/os/os.v
+++ b/vlib/os/os.v
@@ -580,7 +580,7 @@ pub fn get_raw_line() string {
     $if windows {
         max_line_chars := 256
         buf := &byte(malloc(max_line_chars*2))
-        if is_atty(0) {
+        if is_atty(0) > 0 {
             h_input := C.GetStdHandle(STD_INPUT_HANDLE)
             mut nr_chars := 0
             C.ReadConsole(h_input, buf, max_line_chars * 2, &nr_chars, 0)
diff --git a/vlib/term/can_show_color.v b/vlib/term/can_show_color.v
index 2e8ad05631..568280a981 100644
--- a/vlib/term/can_show_color.v
+++ b/vlib/term/can_show_color.v
@@ -3,11 +3,19 @@ module term
 import os
 
 pub fn can_show_color_on_stdout() bool {
-	return is_atty(1) && os.getenv('TERM') != 'dumb'
+	return supports_escape_sequences(1)
 }
 
 pub fn can_show_color_on_stderr() bool {
-	return is_atty(2) && os.getenv('TERM') != 'dumb'
+	return supports_escape_sequences(2)
+}
+
+fn supports_escape_sequences(fd int) bool {
+	$if windows {
+		return (is_atty(fd) & 0x0004) > 0 && os.getenv('TERM') != 'dumb' // ENABLE_VIRTUAL_TERMINAL_PROCESSING
+	} $else {
+		return is_atty(fd) > 0 && os.getenv('TERM') != 'dumb'
+	}
 }
 
 //////////////////////////////////////////////