diff --git a/mrbgems/mruby-bigint/core/bigint.c b/mrbgems/mruby-bigint/core/bigint.c
index 63bd3b24b..06066d736 100644
--- a/mrbgems/mruby-bigint/core/bigint.c
+++ b/mrbgems/mruby-bigint/core/bigint.c
@@ -784,97 +784,6 @@ limb_addmul_1(mp_limb *rp, const mp_limb *s1p, size_t n, mp_limb limb)
 
   return (mp_limb)acc;
 
-#elif defined(_MSC_VER) && defined(MRB_64BIT) && !defined(MRB_NO_MPZ64BIT)
-  /* 64-bit limbs on MSVC with 6x unrolling: use _umul128 */
-  unsigned long long carry = 0;
-  size_t i;
-
-  /* 6x unrolled loop for large operands */
-  for (i = 0; i + 6 <= n; i += 6) {
-    unsigned long long hi, lo, sum;
-
-    lo = _umul128((unsigned long long)s1p[i], (unsigned long long)limb, &hi);
-    unsigned long long rp_val = (unsigned long long)rp[i];
-    unsigned long long temp = rp_val + lo;
-    sum = temp + carry;
-    rp[i] = (mp_limb)sum;
-    carry = hi + (temp < rp_val) + (sum < temp);
-
-    lo = _umul128((unsigned long long)s1p[i+1], (unsigned long long)limb, &hi);
-    unsigned long long rp_val1 = (unsigned long long)rp[i+1];
-    unsigned long long temp1 = rp_val1 + lo;
-    sum = temp1 + carry;
-    rp[i+1] = (mp_limb)sum;
-    carry = hi + (temp1 < rp_val1) + (sum < temp1);
-
-    lo = _umul128((unsigned long long)s1p[i+2], (unsigned long long)limb, &hi);
-    unsigned long long rp_val2 = (unsigned long long)rp[i+2];
-    unsigned long long temp2 = rp_val2 + lo;
-    sum = temp2 + carry;
-    rp[i+2] = (mp_limb)sum;
-    carry = hi + (temp2 < rp_val2) + (sum < temp2);
-
-    lo = _umul128((unsigned long long)s1p[i+3], (unsigned long long)limb, &hi);
-    unsigned long long rp_val3 = (unsigned long long)rp[i+3];
-    unsigned long long temp3 = rp_val3 + lo;
-    sum = temp3 + carry;
-    rp[i+3] = (mp_limb)sum;
-    carry = hi + (temp3 < rp_val3) + (sum < temp3);
-
-    lo = _umul128((unsigned long long)s1p[i+4], (unsigned long long)limb, &hi);
-    unsigned long long rp_val4 = (unsigned long long)rp[i+4];
-    unsigned long long temp4 = rp_val4 + lo;
-    sum = temp4 + carry;
-    rp[i+4] = (mp_limb)sum;
-    carry = hi + (temp4 < rp_val4) + (sum < temp4);
-
-    lo = _umul128((unsigned long long)s1p[i+5], (unsigned long long)limb, &hi);
-    unsigned long long rp_val5 = (unsigned long long)rp[i+5];
-    unsigned long long temp5 = rp_val5 + lo;
-    sum = temp5 + carry;
-    rp[i+5] = (mp_limb)sum;
-    carry = hi + (temp5 < rp_val5) + (sum < temp5);
-  }
-
-  /* 3x unrolled loop for medium operands */
-  for (; i + 3 <= n; i += 3) {
-    unsigned long long hi, lo, sum;
-
-    lo = _umul128((unsigned long long)s1p[i], (unsigned long long)limb, &hi);
-    unsigned long long rp_val = (unsigned long long)rp[i];
-    unsigned long long temp = rp_val + lo;
-    sum = temp + carry;
-    rp[i] = (mp_limb)sum;
-    carry = hi + (temp < rp_val) + (sum < temp);
-
-    lo = _umul128((unsigned long long)s1p[i+1], (unsigned long long)limb, &hi);
-    unsigned long long rp_val1 = (unsigned long long)rp[i+1];
-    unsigned long long temp1 = rp_val1 + lo;
-    sum = temp1 + carry;
-    rp[i+1] = (mp_limb)sum;
-    carry = hi + (temp1 < rp_val1) + (sum < temp1);
-
-    lo = _umul128((unsigned long long)s1p[i+2], (unsigned long long)limb, &hi);
-    unsigned long long rp_val2 = (unsigned long long)rp[i+2];
-    unsigned long long temp2 = rp_val2 + lo;
-    sum = temp2 + carry;
-    rp[i+2] = (mp_limb)sum;
-    carry = hi + (temp2 < rp_val2) + (sum < temp2);
-  }
-
-  /* Handle remaining elements */
-  for (; i < n; i++) {
-    unsigned long long hi, lo;
-    lo = _umul128((unsigned long long)s1p[i], (unsigned long long)limb, &hi);
-    unsigned long long rp_val = (unsigned long long)rp[i];
-    unsigned long long temp = rp_val + lo;
-    unsigned long long sum = temp + carry;
-    rp[i] = (mp_limb)sum;
-    carry = hi + (temp < rp_val) + (sum < temp);
-  }
-
-  return (mp_limb)carry;
-
 #else
   /* Portable double-limb path with 4x unrolling */
   mp_dbl_limb acc = 0;