diff --git a/arch/sim/include/irq.h b/arch/sim/include/irq.h
index 41c9446eb8..efe57f6504 100644
--- a/arch/sim/include/irq.h
+++ b/arch/sim/include/irq.h
@@ -82,7 +82,7 @@ struct xcptcontext
 {
    void *sigdeliver; /* Actual type is sig_deliver_t */
 
-   xcpt_reg_t regs[6];
+   xcpt_reg_t regs[XCPTCONTEXT_REGS];
 };
 #endif
 
@@ -111,7 +111,8 @@ static inline void irqrestore(irqstate_t flags)
 
 #ifdef __cplusplus
 #define EXTERN extern "C"
-extern "C" {
+extern "C"
+{
 #else
 #define EXTERN extern
 #endif
diff --git a/arch/sim/src/up_internal.h b/arch/sim/src/up_internal.h
index dd6b360719..ea20934fcc 100644
--- a/arch/sim/src/up_internal.h
+++ b/arch/sim/src/up_internal.h
@@ -118,8 +118,8 @@
 
 /* Compatibility definitions */
 
-#  define JB_SP    JB_RSI
-#  define JB_PC    JB_RSP
+#  define JB_SP    JB_RSP
+#  define JB_PC    JB_RSI
 
 #else
 /* Storage order: %ebx, $esi, %edi, %ebp, sp, and return PC */