All threads created with CreateThread are 32-bit threads.

diff --git a/scheduler/thread.c b/scheduler/thread.c
index 49d3eec..b9c6ee2 100644
--- a/scheduler/thread.c
+++ b/scheduler/thread.c
@@ -297,6 +297,7 @@
     int handle = -1;
     THDB *thread = THREAD_Create( PROCESS_Current(), flags, stack, TRUE, sa, &handle );
     if (!thread) return INVALID_HANDLE_VALUE;
+    thread->teb.flags  |= TEBF_WIN32;
     thread->entry_point = start;
     thread->entry_arg   = param;
     thread->startup     = THREAD_Start;