diff --git a/ChangeLog b/ChangeLog
index 4ea76d9fe264c1..b35833af0ec40e 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Fri Jan 27 16:31:45 2012  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+
+	* gc.c (HEAP_ALIGN, HEAP_ALIGN_MASK): DRY, let compiler calculate
+	  from HEAP_ALIGN_LOG.
+
 Thu Jan 26 11:03:37 2012  Eric Hodel  <drbrain@segment7.net>
 
 	* lib/matrix.rb:  Clean up extra whitespace in output documentation.
diff --git a/gc.c b/gc.c
index 4c906e7ab23cba..f52b5fc3485b51 100644
--- a/gc.c
+++ b/gc.c
@@ -538,8 +538,8 @@ rb_objspace_free(rb_objspace_t *objspace)
 
 /* tiny heap size: 16KB */
 #define HEAP_ALIGN_LOG 14
-#define HEAP_ALIGN 0x4000
-#define HEAP_ALIGN_MASK 0x3fff
+#define HEAP_ALIGN (1UL << HEAP_ALIGN_LOG)
+#define HEAP_ALIGN_MASK (~(~0UL << HEAP_ALIGN_LOG))
 #define REQUIRED_SIZE_BY_MALLOC (sizeof(size_t) * 5)
 #define HEAP_SIZE (HEAP_ALIGN - REQUIRED_SIZE_BY_MALLOC)