diff --git a/sys/ia64/include/setjmp.h b/sys/ia64/include/setjmp.h
index d7ca9f60ec2b..0e7641eea403 100644
--- a/sys/ia64/include/setjmp.h
+++ b/sys/ia64/include/setjmp.h
@@ -90,11 +90,7 @@
 #define	J_SIGSET	0x1e0
 #endif /* __BSD_VISIBLE */
 
-/*
- * We only have 16 bytes left for future use, but it's a nice round,
- * but above all large number. Size is in bytes.
- */
-#define	_JMPBUFSZ	0x200
+#define	_JBLEN		0x20			/* Size in long doubles */
 
 /*
  * XXX this check is wrong, since LOCORE is in the application namespace and
@@ -113,16 +109,22 @@
  */
 #if __BSD_VISIBLE || __POSIX_VISIBLE || __XSI_VISIBLE
 struct _sigjmp_buf {
-	char	_Buffer[_JMPBUFSZ];
-} __aligned(16);
+	long double buf[_JBLEN];
+};
 typedef struct _sigjmp_buf sigjmp_buf[1];
 #endif
 
 struct _jmp_buf {
-	char	_Buffer[_JMPBUFSZ];
-} __aligned(16);
+	long double buf[_JBLEN];
+};
 typedef struct _jmp_buf	jmp_buf[1];
 
+#ifdef _KERNEL
+#ifdef CTASSERT
+CTASSERT(sizeof(struct _jmp_buf) == 512);
+#endif
+#endif
+
 #endif /* !LOCORE */
 
 #endif /* !_MACHINE_SETJMP_H_ */