diff --git a/ChangeLog b/ChangeLog
index 36ce32aa57a325..fac404b94e3f1e 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Thu Oct 13 19:29:40 2011  Naohisa Goto  <ngotogenome@gmail.com>
+
+	* atomic.h (ATOMIC_*): use atomic_ops(3C) when SunStudio on Solaris.
+	  [ruby-dev:44596] [Bug #5439]
+
 Thu Oct 13 18:13:04 2011  KOSAKI Motohiro  <kosaki.motohiro@gmail.com>
 
 	* atomic.h(ATOMIC_SET): add cast to void to prevent misuse.
diff --git a/atomic.h b/atomic.h
index c770f45d90ca01..d131677aa67fe8 100644
--- a/atomic.h
+++ b/atomic.h
@@ -42,6 +42,16 @@ typedef unsigned int rb_atomic_t; /* Anything OK */
 # define ATOMIC_OR(var, val) __sync_or_and_fetch(&(var), (val))
 # define ATOMIC_EXCHANGE(var, val) __sync_lock_test_and_set(&(var), (val))
 
+#elif defined(__SUNPRO_C)
+#include <atomic.h>
+typedef unsigned int rb_atomic_t;
+
+# define ATOMIC_SET(var, val) (void)atomic_swap_uint(&(var), (val))
+# define ATOMIC_INC(var) atomic_inc_uint(&(var))
+# define ATOMIC_DEC(var) atomic_dec_uint(&(var))
+# define ATOMIC_OR(var, val) atomic_or_uint(&(var), (val))
+# define ATOMIC_EXCHANGE(var, val) atomic_swap_uint(&(var), (val))
+
 #else
 typedef int rb_atomic_t;
 extern rb_atomic_t ruby_atomic_exchange(rb_atomic_t *ptr, rb_atomic_t val);