diff --git a/ChangeLog b/ChangeLog
index 269989eb56..fb7259d630 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,9 @@
+Mon May 27 22:09:33 2013  Tanaka Akira  <akr@fsij.org>
+
+	* include/ruby/ruby.h (RHASH_SIZE): Add a cast to suppress a
+	  warning, comparison between signed and unsigned integer
+	  expressions [-Wsign-compare], on ILP32.
+
 Mon May 27 19:25:47 2013  Koichi Sasada  <ko1@atdot.net>
 
 	* include/ruby/ruby.h: rename RUBY_INTERNAL_EVENT_FREE to
diff --git a/include/ruby/ruby.h b/include/ruby/ruby.h
index 03440bf16a..d632f57226 100644
--- a/include/ruby/ruby.h
+++ b/include/ruby/ruby.h
@@ -971,7 +971,7 @@ struct RHash {
 #define RHASH_TBL(h) rb_hash_tbl(h)
 #define RHASH_ITER_LEV(h) (RHASH(h)->iter_lev)
 #define RHASH_IFNONE(h) (RHASH(h)->ifnone)
-#define RHASH_SIZE(h) (RHASH(h)->ntbl ? RHASH(h)->ntbl->num_entries : 0)
+#define RHASH_SIZE(h) (RHASH(h)->ntbl ? (st_index_t)RHASH(h)->ntbl->num_entries : 0)
 #define RHASH_EMPTY_P(h) (RHASH_SIZE(h) == 0)
 #define RHASH_SET_IFNONE(h, ifnone) rb_hash_set_ifnone((VALUE)h, ifnone)