diff --git a/lib/std/os.zig b/lib/std/os.zig
index 12cda72e400a..1e99efc44c91 100644
--- a/lib/std/os.zig
+++ b/lib/std/os.zig
@@ -5338,11 +5338,13 @@ pub fn getFdPath(fd: fd_t, out_buffer: *[MAX_PATH_BYTES]u8) RealPathError![]u8 {
     }
 }
 
+const nanosize = if (is_windows) c_long else isize;
+
 /// Spurious wakeups are possible and no precision of timing is guaranteed.
 pub fn nanosleep(seconds: u64, nanoseconds: u64) void {
     var req = timespec{
         .tv_sec = math.cast(isize, seconds) orelse math.maxInt(isize),
-        .tv_nsec = math.cast(isize, nanoseconds) orelse math.maxInt(isize),
+        .tv_nsec = math.cast(nanosize, nanoseconds) orelse math.maxInt(nanosize),
     };
     var rem: timespec = undefined;
     while (true) {