diff --git a/arch/ia64/lib/memcpy_mck.S b/arch/ia64/lib/memcpy_mck.S
index 6f308e62c1377cc04ee24efcd08775a66ed24dae..46c9331e7ab5f81181b5e19745c154a80c4b852e 100644
--- a/arch/ia64/lib/memcpy_mck.S
+++ b/arch/ia64/lib/memcpy_mck.S
@@ -625,8 +625,11 @@ EK(.ex_handler,  (p17)	st8	[dst1]=r39,8);						\
 	clrrrb
 	;;
 	alloc	saved_pfs_stack=ar.pfs,3,3,3,0
+	cmp.lt	p8,p0=A,r0
 	sub	B = dst0, saved_in0	// how many byte copied so far
 	;;
+(p8)	mov	A = 0;			// A shouldn't be negative, cap it
+	;;
 	sub	C = A, B
 	sub	D = saved_in2, A
 	;;