diff --git a/arch/x86/core/ia32/crt0.S b/arch/x86/core/ia32/crt0.S
index e611c884274..1f431489bfe 100644
--- a/arch/x86/core/ia32/crt0.S
+++ b/arch/x86/core/ia32/crt0.S
@@ -240,6 +240,7 @@ __csSet:
 #endif
 
 	pushl	%ebx		/* pointer to multiboot info, or NULL */
+	pushl	%eax		/* junk, unused argument */
 	call	z_x86_prep_c	/* enter kernel; never returns */
 
 _x86_bss_zero:
diff --git a/arch/x86/core/intel64/cpu.c b/arch/x86/core/intel64/cpu.c
index 15cd04e6463..751373c2143 100644
--- a/arch/x86/core/intel64/cpu.c
+++ b/arch/x86/core/intel64/cpu.c
@@ -9,7 +9,7 @@
 #include <kernel_structs.h>
 #include <arch/x86/multiboot.h>
 
-extern FUNC_NORETURN void z_x86_prep_c(struct multiboot_info *);
+extern FUNC_NORETURN void z_x86_prep_c(int, struct multiboot_info *);
 
 extern u8_t _exception_stack[];
 
diff --git a/arch/x86/core/intel64/locore.S b/arch/x86/core/intel64/locore.S
index 2a065239e91..58bf6b031b6 100644
--- a/arch/x86/core/intel64/locore.S
+++ b/arch/x86/core/intel64/locore.S
@@ -104,7 +104,7 @@ __start:
 
 	/* don't replace CALL with JMP; honor the ABI stack alignment! */
 
-	movq __x86_cpuboot_t_arg_OFFSET(%rbp), %rdi
+	movq __x86_cpuboot_t_arg_OFFSET(%rbp), %rsi
 	call *__x86_cpuboot_t_fn_OFFSET(%rbp) /* enter kernel; never return */
 
 /*
diff --git a/arch/x86/core/prep_c.c b/arch/x86/core/prep_c.c
index 6c3b22e5f46..b7ce0777330 100644
--- a/arch/x86/core/prep_c.c
+++ b/arch/x86/core/prep_c.c
@@ -10,8 +10,10 @@
 
 extern FUNC_NORETURN void z_cstart(void);
 
-FUNC_NORETURN void z_x86_prep_c(struct multiboot_info *info)
+FUNC_NORETURN void z_x86_prep_c(int unused, struct multiboot_info *info)
 {
+	ARG_UNUSED(unused);
+
 	_kernel.cpus[0].nested = 0;
 	_kernel.cpus[0].irq_stack = Z_THREAD_STACK_BUFFER(_interrupt_stack) +
 					CONFIG_ISR_STACK_SIZE;