diff --git a/ChangeLog b/ChangeLog
index 7403694b17..1927ff74a4 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Sun Jun 23 07:41:52 2013  Tanaka Akira  <akr@fsij.org>
+
+	* bignum.c (bary_unpack_internal): Suppress warnings (C4146) on Visual Studio.
+	  Reported by ko1 via IRC.
+
 Sun Jun 23 06:49:28 2013  Koichi Sasada  <ko1@atdot.net>
 
 	* include/ruby/ruby.h, gc.c: rename macros and functions:
diff --git a/bignum.c b/bignum.c
index b8bcedc7ac..21a03df314 100644
--- a/bignum.c
+++ b/bignum.c
@@ -1364,7 +1364,7 @@ bary_unpack_internal(BDIGIT *bdigits, size_t num_bdigits, const void *words, siz
                     sign = (flags & INTEGER_PACK_NEGATIVE) ?
                         ((sizeof(uint8_t) == SIZEOF_BDIGITS && u == 0) ? -2 : -1) :
                         ((u >> (sizeof(uint8_t) * CHAR_BIT - 1)) ? -1 : 1);
-                    if (sign < 0) u = -(u | LSHIFTX((~(BDIGIT)0), sizeof(uint8_t) * CHAR_BIT));
+                    if (sign < 0) u = ((BDIGIT)0) - (u | LSHIFTX((~(BDIGIT)0), sizeof(uint8_t) * CHAR_BIT));
                 }
                 else
                     sign = (flags & INTEGER_PACK_NEGATIVE) ? -1 : 1;
@@ -1379,7 +1379,7 @@ bary_unpack_internal(BDIGIT *bdigits, size_t num_bdigits, const void *words, siz
                     sign = (flags & INTEGER_PACK_NEGATIVE) ?
                         ((sizeof(uint16_t) == SIZEOF_BDIGITS && u == 0) ? -2 : -1) :
                         ((u >> (sizeof(uint16_t) * CHAR_BIT - 1)) ? -1 : 1);
-                    if (sign < 0) u = -(u | LSHIFTX((~(BDIGIT)0), sizeof(uint16_t) * CHAR_BIT));
+                    if (sign < 0) u = ((BDIGIT)0) - (u | LSHIFTX((~(BDIGIT)0), sizeof(uint16_t) * CHAR_BIT));
                 }
                 else
                     sign = (flags & INTEGER_PACK_NEGATIVE) ? -1 : 1;
@@ -1395,7 +1395,7 @@ bary_unpack_internal(BDIGIT *bdigits, size_t num_bdigits, const void *words, siz
                     sign = (flags & INTEGER_PACK_NEGATIVE) ?
                         ((sizeof(uint32_t) == SIZEOF_BDIGITS && u == 0) ? -2 : -1) :
                         ((u >> (sizeof(uint32_t) * CHAR_BIT - 1)) ? -1 : 1);
-                    if (sign < 0) u = -(u | LSHIFTX((~(BDIGIT)0), sizeof(uint32_t) * CHAR_BIT));
+                    if (sign < 0) u = ((BDIGIT)0) - (u | LSHIFTX((~(BDIGIT)0), sizeof(uint32_t) * CHAR_BIT));
                 }
                 else
                     sign = (flags & INTEGER_PACK_NEGATIVE) ? -1 : 1;
@@ -1411,7 +1411,7 @@ bary_unpack_internal(BDIGIT *bdigits, size_t num_bdigits, const void *words, siz
                     sign = (flags & INTEGER_PACK_NEGATIVE) ?
                         ((sizeof(uint64_t) == SIZEOF_BDIGITS && u == 0) ? -2 : -1) :
                         ((u >> (sizeof(uint64_t) * CHAR_BIT - 1)) ? -1 : 1);
-                    if (sign < 0) u = -(u | LSHIFTX((~(BDIGIT)0), sizeof(uint64_t) * CHAR_BIT));
+                    if (sign < 0) u = ((BDIGIT)0) - (u | LSHIFTX((~(BDIGIT)0), sizeof(uint64_t) * CHAR_BIT));
                 }
                 else
                     sign = (flags & INTEGER_PACK_NEGATIVE) ? -1 : 1;