diff --git a/vlib/builtin/builtin_windows.c.v b/vlib/builtin/builtin_windows.c.v
index 6d34fa23af..0f0cd8165d 100644
--- a/vlib/builtin/builtin_windows.c.v
+++ b/vlib/builtin/builtin_windows.c.v
@@ -7,7 +7,25 @@ module builtin
 // g_original_codepage - used to restore the original windows console code page when exiting
 __global g_original_codepage = u32(0)
 
-type C.BOOL = bool
+pub type C.BOOL = bool
+
+pub struct C.HINSTANCE {}
+
+pub struct C.HICON {}
+
+pub struct C.HCURSOR {}
+
+pub struct C.HCURSOR {}
+
+pub struct C.HBRUSH {}
+
+pub struct C.HWND {}
+
+pub struct C.HGLOBAL {}
+
+pub struct C.HANDLE {}
+
+pub struct C.LRESULT {}
 
 // utf8 to stdout needs C.SetConsoleOutputCP(cp_utf8)
 fn C.GetConsoleOutputCP() u32
diff --git a/vlib/clipboard/clipboard_windows.c.v b/vlib/clipboard/clipboard_windows.c.v
index 9eab9f62f9..44489250f8 100644
--- a/vlib/clipboard/clipboard_windows.c.v
+++ b/vlib/clipboard/clipboard_windows.c.v
@@ -110,7 +110,7 @@ fn new_clipboard() &Clipboard {
 
 // check_availability returns true if the clipboard is ready to be used.
 pub fn (cb &Clipboard) check_availability() bool {
-	return cb.hwnd != C.HWND(C.NULL)
+	return cb.hwnd != unsafe { nil }
 }
 
 // has_ownership returns true if the contents of
@@ -143,7 +143,7 @@ fn to_wide(text string) C.HGLOBAL {
 	len_required := C.MultiByteToWideChar(clipboard.cp_utf8, C.MB_ERR_INVALID_CHARS, text.str,
 		text.len + 1, C.NULL, 0)
 	buf := C.GlobalAlloc(C.GMEM_MOVEABLE, i64(sizeof(u16)) * len_required)
-	if buf != C.HGLOBAL(C.NULL) {
+	if buf != unsafe { nil } {
 		mut locked := &u16(C.GlobalLock(buf))
 		C.MultiByteToWideChar(clipboard.cp_utf8, C.MB_ERR_INVALID_CHARS, text.str, text.len + 1,
 			locked, len_required)
@@ -166,7 +166,7 @@ pub fn (mut cb Clipboard) set_text(text string) bool {
 	} else {
 		// EmptyClipboard must be called to properly update clipboard ownership
 		C.EmptyClipboard()
-		if C.SetClipboardData(C.CF_UNICODETEXT, buf) == C.HANDLE(C.NULL) {
+		if C.SetClipboardData(C.CF_UNICODETEXT, buf) == unsafe { nil } {
 			println('SetClipboardData: Failed.')
 			C.CloseClipboard()
 			C.GlobalFree(buf)
@@ -187,7 +187,7 @@ pub fn (mut cb Clipboard) get_text() string {
 		return ''
 	}
 	h_data := C.GetClipboardData(C.CF_UNICODETEXT)
-	if h_data == C.HANDLE(C.NULL) {
+	if h_data == unsafe { nil } {
 		C.CloseClipboard()
 		return ''
 	}
diff --git a/vlib/net/http/backend_windows.c.v b/vlib/net/http/backend_windows.c.v
index c938bdfc7c..5a758bb0cc 100644
--- a/vlib/net/http/backend_windows.c.v
+++ b/vlib/net/http/backend_windows.c.v
@@ -11,6 +11,8 @@ $if gcboehm ? {
 #flag -l ws2_32 -l crypt32 -l secur32 -l user32
 #include "vschannel.c"
 
+struct C.TlsContext {}
+
 fn C.new_tls_context() C.TlsContext
 
 fn (req &Request) ssl_do(port int, method Method, host_name string, path string) !Response {