diff --git a/efi_types.h b/efi_types.h
index b4e5bbd..e7ca151 100644
--- a/efi_types.h
+++ b/efi_types.h
@@ -35,6 +35,11 @@ typedef unsigned long UINTPTR;
 typedef long SSIZE;
 typedef unsigned long SIZE;
 
+typedef __builtin_va_list VA_LIST;
+#define va_start(ap, arg) __builtin_va_start(ap, arg)
+#define va_arg(ap, type) __builtin_va_arg(ap, type)
+#define va_end(ap) __builtin_va_end(ap)
+
 typedef UINTN EFI_STATUS;
 typedef VOID *EFI_HANDLE;
 typedef VOID *EFI_EVENT;