diff --git a/hermit/arch/x86/include/asm/processor.h b/hermit/arch/x86/include/asm/processor.h
index 454ff0881..03fad09be 100644
--- a/hermit/arch/x86/include/asm/processor.h
+++ b/hermit/arch/x86/include/asm/processor.h
@@ -656,7 +656,7 @@ void udelay(uint32_t usecs);
 /// Register a task's TSS at GDT
 static inline void register_task(void)
 {
-	uint16_t sel = (CORE_ID*2+7) << 3;
+	uint16_t sel = (apic_cpu_id()*2+7) << 3;
 
 	asm volatile ("ltr %%ax" : : "a"(sel));
 }