diff --git a/am/include/x86.h b/am/include/x86.h
index 5341c841..bc78fa0e 100644
--- a/am/include/x86.h
+++ b/am/include/x86.h
@@ -47,6 +47,7 @@
 #define EX_PF          14
 #define EX_MF          15
 #define EX_SYSCALL     0x80
+#define EX_YIELD       0x81
 
 // List of interrupts and exceptions (#irq, DPL, hardware errorcode)
 #define IRQS(_) \
@@ -85,7 +86,8 @@
   _( 45, KERN, NOERR) \
   _( 46, KERN, NOERR) \
   _( 47, KERN, NOERR) \
-  _(128, USER, NOERR)
+  _(128, USER, NOERR) \
+  _(129, USER, NOERR)
 
 // AM-specific configurations
 #define MAX_CPU       8
@@ -330,8 +332,8 @@ static inline uint64_t rdtsc() {
   return ((uint64_t)hi << 32) | lo;
 }
 
-#define interrupt(id, ax) \
-  asm volatile ("int $" #id : : "a"(ax));
+#define interrupt(id) \
+  asm volatile ("int $" #id);
 
 static inline void stack_switch_call(void *sp, void *entry, uintptr_t arg) {
   asm volatile (
diff --git a/am/src/x86/qemu/cte.c b/am/src/x86/qemu/cte.c
index 880b4660..ca92fce7 100644
--- a/am/src/x86/qemu/cte.c
+++ b/am/src/x86/qemu/cte.c
@@ -57,13 +57,10 @@ static void __am_irq_handle_internal(struct trap_frame *tf) {
       ev.event = _EVENT_IRQ_TIMER; break;
     case IRQ 1: MSG("I/O device IRQ1 (keyboard)")
       ev.event = _EVENT_IRQ_IODEV; break;
-    case EX_SYSCALL: MSG("int $0x80 trap: _yield() or system call")
-      if ((int32_t)saved_ctx.GPRx == -1) {
-        ev.event = _EVENT_YIELD;
-      } else {
-        ev.event = _EVENT_SYSCALL;
-      }
-      break;
+    case EX_SYSCALL: MSG("int $0x80 system call")
+      ev.event = _EVENT_SYSCALL; break;
+    case EX_YIELD: MSG("int $0x81 yield")
+      ev.event = _EVENT_YIELD; break;
     case EX_DE: MSG("DE #0 divide by zero")
       ev.event = _EVENT_ERROR; break;
     case EX_UD: MSG("UD #6 invalid opcode")
@@ -129,7 +126,7 @@ int _cte_init(_Context *(*handler)(_Event, _Context *)) {
 }
 
 void _yield() {
-  interrupt(0x80, -1);
+  interrupt(0x81);
 }
 
 int _intr_read() {