diff --git a/arch/x86_64/src/intel64/intel64_cpuidlestack.c b/arch/x86_64/src/intel64/intel64_cpuidlestack.c
index 05d8771b43c28..e9aec20395628 100644
--- a/arch/x86_64/src/intel64/intel64_cpuidlestack.c
+++ b/arch/x86_64/src/intel64/intel64_cpuidlestack.c
@@ -88,7 +88,8 @@ int up_cpu_idlestack(int cpu, struct tcb_s *tcb, size_t stack_size)
 
   /* Get the top of the stack */
 
-  stack_alloc          = (uintptr_t)g_idle_topstack[cpu];
+  stack_alloc          = (uintptr_t)g_idle_topstack[cpu] -
+                         CONFIG_IDLETHREAD_STACKSIZE;
   tcb->adj_stack_size  = stack_size - 8;
   tcb->stack_alloc_ptr = (void *)stack_alloc;
   tcb->stack_base_ptr  = tcb->stack_alloc_ptr;
diff --git a/arch/x86_64/src/intel64/intel64_head.S b/arch/x86_64/src/intel64/intel64_head.S
index 9b0cf93705e24..488f487fa697d 100644
--- a/arch/x86_64/src/intel64/intel64_head.S
+++ b/arch/x86_64/src/intel64/intel64_head.S
@@ -392,6 +392,10 @@ ap_start:
 	add     %rax, %rbx
 	mov     (%rbx),   %rsp
 
+	/* Move initial RSP below IDLE TCB regs */
+	sub     $XCPTCONTEXT_SIZE, %rsp
+	and     $(~XCPTCONTEXT_SIZE), %rsp
+
 	/* Jump to ap_start routine */
 	movabs  $x86_64_ap_boot,   %rbx
 	jmp     *%rbx
diff --git a/arch/x86_64/src/intel64/intel64_schedulesigaction.c b/arch/x86_64/src/intel64/intel64_schedulesigaction.c
index 0763b2cab5bf8..d846ed3798a73 100644
--- a/arch/x86_64/src/intel64/intel64_schedulesigaction.c
+++ b/arch/x86_64/src/intel64/intel64_schedulesigaction.c
@@ -130,6 +130,7 @@ void up_schedule_sigaction(struct tcb_s *tcb, sig_deliver_t sigdeliver)
                */
 
               up_current_regs()[REG_RIP]    = (uint64_t)x86_64_sigdeliver;
+              up_current_regs()[REG_RSP]    = up_current_regs()[REG_RSP] - 8;
               up_current_regs()[REG_RFLAGS] = 0;
 
               /* And make sure that the saved context in the TCB
@@ -162,6 +163,7 @@ void up_schedule_sigaction(struct tcb_s *tcb, sig_deliver_t sigdeliver)
            */
 
           tcb->xcp.regs[REG_RIP]    = (uint64_t)x86_64_sigdeliver;
+          tcb->xcp.regs[REG_RSP]    = tcb->xcp.regs[REG_RSP] - 8;
           tcb->xcp.regs[REG_RFLAGS] = 0;
         }
     }
@@ -242,6 +244,7 @@ void up_schedule_sigaction(struct tcb_s *tcb, sig_deliver_t sigdeliver)
                    */
 
                   tcb->xcp.regs[REG_RIP]    = (uint64_t)x86_64_sigdeliver;
+                  tcb->xcp.regs[REG_RSP]    = tcb->xcp.regs[REG_RSP] - 8;
                   tcb->xcp.regs[REG_RFLAGS] = 0;
                 }
               else
@@ -261,7 +264,10 @@ void up_schedule_sigaction(struct tcb_s *tcb, sig_deliver_t sigdeliver)
                    * disabled
                    */
 
-                  up_current_regs()[REG_RIP]  = (uint64_t)x86_64_sigdeliver;
+                  up_current_regs()[REG_RIP]    =
+                    (uint64_t)x86_64_sigdeliver;
+                  up_current_regs()[REG_RSP]    =
+                    up_current_regs()[REG_RSP] - 8;
                   up_current_regs()[REG_RFLAGS] = 0;
 
                   /* And make sure that the saved context in the TCB
@@ -308,6 +314,7 @@ void up_schedule_sigaction(struct tcb_s *tcb, sig_deliver_t sigdeliver)
            */
 
           tcb->xcp.regs[REG_RIP]    = (uint64_t)x86_64_sigdeliver;
+          tcb->xcp.regs[REG_RSP]    = tcb->xcp.regs[REG_RSP] - 8;
           tcb->xcp.regs[REG_RFLAGS] = 0;
         }
     }