diff --git a/sys/amd64/machine.c b/sys/amd64/machine.c
index 9c97d7d..e1e125e 100644
--- a/sys/amd64/machine.c
+++ b/sys/amd64/machine.c
@@ -4,6 +4,7 @@
 #include <kconfig.h>
 #include <kassert.h>
 #include <kmem.h>
+#include <irq.h>
 
 #include "amd64.h"
 #include "ioapic.h"
@@ -76,7 +77,7 @@ void Machine_SyscallInit()
 {
     kprintf("Initializing Syscall... ");
 
-    wrmsr(MSR_STAR, SEL_KCS << 32 | SEL_UCS << 48);
+    wrmsr(MSR_STAR, (uint64_t)SEL_KCS << 32 | (uint64_t)SEL_UCS << 48);
     wrmsr(MSR_LSTAR, 0);
     wrmsr(MSR_CSTAR, 0);
     wrmsr(MSR_SFMASK, 0);