diff --git a/linux-user/syscall_defs.h b/linux-user/syscall_defs.h
index ebb3be1196..9ed6de88ec 100644
--- a/linux-user/syscall_defs.h
+++ b/linux-user/syscall_defs.h
@@ -655,7 +655,14 @@ typedef struct {
 #endif
 
 #define TARGET_SI_MAX_SIZE	128
-#define TARGET_SI_PAD_SIZE	((TARGET_SI_MAX_SIZE/sizeof(int)) - 3)
+
+#if TARGET_ABI_BITS == 32
+#define TARGET_SI_PREAMBLE_SIZE (3 * sizeof(int))
+#else
+#define TARGET_SI_PREAMBLE_SIZE (4 * sizeof(int))
+#endif
+
+#define TARGET_SI_PAD_SIZE ((TARGET_SI_MAX_SIZE - TARGET_SI_PREAMBLE_SIZE) / sizeof(int))
 
 typedef struct target_siginfo {
 #ifdef TARGET_MIPS