diff --git a/tools/cpu/unix/gensize.c b/tools/cpu/unix/gensize.c
index 41c28bbf52..2d848e0a94 100644
--- a/tools/cpu/unix/gensize.c
+++ b/tools/cpu/unix/gensize.c
@@ -36,6 +36,7 @@
 typedef struct {
   jmp_buf     regs;
   int         isr_level;
+  int         pad[4]; /* just in case */
 } Context_Control;
 
 int main(