diff --git a/service/ptos/arch/amd64/ps/thread.c b/service/ptos/arch/amd64/ps/thread.c
index 996ffc8..b831fe7 100644
--- a/service/ptos/arch/amd64/ps/thread.c
+++ b/service/ptos/arch/amd64/ps/thread.c
@@ -145,6 +145,12 @@ HalThreadInit(THREAD *Thread, ULONG Flags, UPTR Ip)
     return STATUS_SUCCESS;
 }
 
+VOID
+HalThreadYield(VOID)
+{
+    asm volatile("int $0x81");
+}
+
 VOID
 HalPrimeThreadTimer(ULONG Usec)
 {
diff --git a/service/ptos/head/hal/thread.h b/service/ptos/head/hal/thread.h
index ce90b39..af5ab66 100644
--- a/service/ptos/head/hal/thread.h
+++ b/service/ptos/head/hal/thread.h
@@ -22,6 +22,11 @@
  */
 PT_STATUS HalThreadInit(THREAD *Thread, ULONG Flags, UPTR Ip);
 
+/*
+ * Yield the current thread
+ */
+VOID HalThreadYield(VOID);
+
 /*
  * Prime the scheduler timer
  *