diff --git a/lib/std/os/uefi.zig b/lib/std/os/uefi.zig
index 165c3df249..91f3678b26 100644
--- a/lib/std/os/uefi.zig
+++ b/lib/std/os/uefi.zig
@@ -26,9 +26,9 @@ pub var system_table: *tables.SystemTable = undefined;
 pub const Event = *opaque {};
 
 /// The calling convention used for all external functions part of the UEFI API.
-pub const cc = switch (@import("builtin").target.cpu.arch) {
-    .x86_64 => .Win64,
-    else => .C,
+pub const cc: std.builtin.CallingConvention = switch (@import("builtin").target.cpu.arch) {
+    .x86_64 => .{ .x86_64_win = .{} },
+    else => .c,
 };
 
 pub const MacAddress = extern struct {