diff --git a/src/drivers/nulldrv/main.s b/src/drivers/nulldrv/main.s
index d6973f6..c280013 100644
--- a/src/drivers/nulldrv/main.s
+++ b/src/drivers/nulldrv/main.s
@@ -2,9 +2,9 @@ global _start
 _start:
 	xor rbp, rbp	; Sentinel rbp
 
-	mov rdi, 0		; DEBUG syscall
-
 .loop:
+	mov rax, 0		; DEBUG syscall
 	syscall
+
 	jmp .loop
 
diff --git a/src/kernel/interrupts.cpp b/src/kernel/interrupts.cpp
index b3b836c..c560cfb 100644
--- a/src/kernel/interrupts.cpp
+++ b/src/kernel/interrupts.cpp
@@ -303,12 +303,9 @@ addr_t
 syscall_handler(addr_t return_rsp, cpu_state regs)
 {
 	console *cons = console::get();
-	syscall call = static_cast<syscall>(regs.rdi & 0xffff);
+	syscall call = static_cast<syscall>(regs.rax);
 
 	switch (call) {
-	case syscall::message:
-		break;
-
 	case syscall::debug:
 		cons->set_color(11);
 		cons->printf("\nReceived DEBUG syscall\n");
@@ -316,6 +313,9 @@ syscall_handler(addr_t return_rsp, cpu_state regs)
 		print_regs(regs);
 		break;
 
+	case syscall::message:
+		break;
+
 	default:
 		cons->set_color(9);
 		cons->printf("\nReceived unknown syscall: %02x\n", call);
diff --git a/src/kernel/syscall.h b/src/kernel/syscall.h
index 72bfc06..6513785 100644
--- a/src/kernel/syscall.h
+++ b/src/kernel/syscall.h
@@ -1,6 +1,6 @@
 #pragma once
 
-enum class syscall : uint16_t
+enum class syscall : uint64_t
 {
 	debug,
 	message,