diff --git a/lib/srfi/142/bit.c b/lib/srfi/142/bit.c
index 3dae9eab..bb5c67b1 100644
--- a/lib/srfi/142/bit.c
+++ b/lib/srfi/142/bit.c
@@ -164,17 +164,17 @@ sexp sexp_bit_xor (sexp ctx, sexp self, sexp_sint_t n, sexp x, sexp y) {
 #if SEXP_USE_BIGNUMS
   } else if (sexp_bignump(x)) {
     sexp_gc_preserve2(ctx, res, tmp);
-    if (sexp_fixnump(y)) {
+    if (sexp_fixnump(y) && sexp_unbox_fixnum(y) >= 0) {
       res = sexp_copy_bignum(ctx, NULL, x, 0);
       if (sexp_bignum_sign(res) < 0)
         sexp_set_twos_complement(res);
       sexp_bignum_data(res)[0] ^= sexp_unbox_fixnum(y);
       if (sexp_bignum_sign(res) < 0)
         sexp_set_twos_complement(res);
-    } else if (sexp_bignump(y)) {
-      if (sexp_bignum_length(x) >= sexp_bignum_length(y)) {
+    } else if (sexp_bignump(y) || sexp_fixnump(y)) {
+      if (sexp_fixnump(y) || sexp_bignum_length(x) >= sexp_bignum_length(y)) {
         res = sexp_copy_bignum(ctx, NULL, x, 0);
-        tmp = sexp_twos_complement(ctx, y);
+        tmp = sexp_fixnump(y) ? sexp_fixnum_to_twos_complement(ctx, y, sexp_bignum_length(x)) : sexp_twos_complement(ctx, y);
         len = sexp_bignum_length(tmp);
       } else {
         res = sexp_copy_bignum(ctx, NULL, y, 0);
@@ -186,10 +186,9 @@ sexp sexp_bit_xor (sexp ctx, sexp self, sexp_sint_t n, sexp x, sexp y) {
       for (i=0; i<len; i++)
         sexp_bignum_data(res)[i]
           = sexp_bignum_data(res)[i] ^ sexp_bignum_data(tmp)[i];
-      if (sexp_bignum_sign(res) < 0)
-        sexp_set_twos_complement(res);
-      if  (!((sexp_bignum_sign(x) < 0) ^ (sexp_bignum_sign(y) < 0))) {
+      if ((sexp_bignum_sign(x) < 0) ^ (sexp_fixnump(y) || sexp_bignum_sign(y) < 0))
         sexp_set_twos_complement(res);
+      if (sexp_fixnump(y) || sexp_bignum_sign(y) < 0) {
         sexp_negate_exact(res);
       }
     } else {
diff --git a/lib/srfi/142/test.sld b/lib/srfi/142/test.sld
index 55db18b3..ff123055 100644
--- a/lib/srfi/142/test.sld
+++ b/lib/srfi/142/test.sld
@@ -28,6 +28,8 @@
                        1689392892000000000000193073517000000000000))
       (test -2604237975 (bitwise-xor 1694076839 -4290775858))
       (test -1865418641 (bitwise-xor -193073517 1689392892))
+      (test -1689392892000142479725
+          (bitwise-xor -193073517 1689392892000000000000))
       (test -1510500507664429879296
           (bitwise-xor -193073517000000000000 1689392892000000000000))
       (test -1510500507664429879296
@@ -35,6 +37,9 @@
       (test -461856550205267621490541042387407516495872
           (bitwise-xor -1930735170000000000001689392892000000000000
                        1689392892000000000000193073517000000000000))
+      (test -461856550205267621490541042387407516495872
+          (bitwise-xor 1689392892000000000000193073517000000000000
+                       -1930735170000000000001689392892000000000000))
       (test 461856550205267621490541042387407516495872
           (bitwise-xor -1930735170000000000001689392892000000000000
                        -1689392892000000000000193073517000000000000))