diff --git a/ChangeLog b/ChangeLog
index dc6d12dafe..f7be7959d2 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,9 @@
+Thu Jun 13 06:12:18 2013  Tanaka Akira  <akr@fsij.org>
+
+	* bignum.c (integer_unpack_num_bdigits_small): Fix a comple error on
+	  clang -Werror,-Wshorten-64-to-32
+	  Reported by Eric Hodel.  [ruby-core:55467] [Bug #8522]
+
 Thu Jun 13 05:32:13 2013  Eric Hodel  <drbrain@segment7.net>
 
 	* ext/socket/extconf.rb:  Enable RFC 3542 IPV6 socket options for OS X
diff --git a/bignum.c b/bignum.c
index ab5bf59201..ba786489aa 100644
--- a/bignum.c
+++ b/bignum.c
@@ -1125,7 +1125,7 @@ integer_unpack_num_bdigits_small(size_t numwords, size_t wordsize, size_t nails,
     /* nlp_bits stands for number of leading padding bits */
     size_t num_bits = (wordsize * CHAR_BIT - nails) * numwords;
     size_t num_bdigits = (num_bits + BITSPERDIG - 1) / BITSPERDIG;
-    *nlp_bits_ret = num_bdigits * BITSPERDIG - num_bits;
+    *nlp_bits_ret = (int)(num_bdigits * BITSPERDIG - num_bits);
     return num_bdigits;
 }
 
@@ -1224,7 +1224,7 @@ rb_integer_unpack_internal(const void *words, size_t numwords, size_t wordsize,
     BDIGIT_DBL dd;
     int numbits_in_dd;
 
-    if (numwords <= (SIZE_MAX - (SIZEOF_BDIGITS*CHAR_BIT-1)) / CHAR_BIT / wordsize) {
+    if (numwords <= (SIZE_MAX - (BITSPERDIG-1)) / CHAR_BIT / wordsize) {
         num_bdigits = integer_unpack_num_bdigits_small(numwords, wordsize, nails, nlp_bits_ret);
 #if 0
         {