diff --git a/crypto/bn/bn_shift.c b/crypto/bn/bn_shift.c
index 61aae65a6..088324738 100644
--- a/crypto/bn/bn_shift.c
+++ b/crypto/bn/bn_shift.c
@@ -162,7 +162,7 @@ int BN_rshift(BIGNUM *r, BIGNUM *a, int n)
 	nw=n/BN_BITS2;
 	rb=n%BN_BITS2;
 	lb=BN_BITS2-rb;
-	if (nw > a->top)
+	if (nw > a->top || a->top == 0)
 		{
 		BN_zero(r);
 		return(1);