diff --git a/library/std/src/sys/windows/thread.rs b/library/std/src/sys/windows/thread.rs
index e4bba9255d2..fdbf7d4fded 100644
--- a/library/std/src/sys/windows/thread.rs
+++ b/library/std/src/sys/windows/thread.rs
@@ -28,12 +28,9 @@ impl Thread {
         // PTHREAD_STACK_MIN bytes big.  Windows has no such lower limit, it's
         // just that below a certain threshold you can't do anything useful.
         // That threshold is application and architecture-specific, however.
-        // Round up to the next 64 kB because that's what the NT kernel does,
-        // might as well make it explicit.
-        let stack_size = (stack + 0xfffe) & (!0xfffe);
         let ret = c::CreateThread(
             ptr::null_mut(),
-            stack_size,
+            stack,
             thread_start,
             p as *mut _,
             c::STACK_SIZE_PARAM_IS_A_RESERVATION,