diff --git a/ChangeLog b/ChangeLog
index 8c2b3b3861..2614ec5af9 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,7 @@
+Tue Feb 14 20:22:11 2012  Narihiro Nakamura  <authornari@gmail.com>
+
+	* gc.c (CEILDIV): rename to a appropriate name.
+
 Tue Feb 14 18:07:20 2012  Narihiro Nakamura  <authornari@gmail.com>
 
 	* gc.c (assign_heap_slot): SEGV happens cause on 64-bit platform
diff --git a/gc.c b/gc.c
index 12dbb115f9..cbc95ddb26 100644
--- a/gc.c
+++ b/gc.c
@@ -544,10 +544,10 @@ rb_objspace_free(rb_objspace_t *objspace)
 #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)
-#define CEILMOD(i, mod) (((i) + (mod) - 1)/(mod))
+#define CEILDIV(i, mod) (((i) + (mod) - 1)/(mod))
 
 #define HEAP_OBJ_LIMIT (unsigned int)((HEAP_SIZE - sizeof(struct heaps_header))/sizeof(struct RVALUE))
-#define HEAP_BITMAP_LIMIT CEILMOD(HEAP_OBJ_LIMIT, sizeof(uintptr_t)*8)
+#define HEAP_BITMAP_LIMIT CEILDIV(HEAP_OBJ_LIMIT, sizeof(uintptr_t)*8)
 
 #define GET_HEAP_HEADER(x) (HEAP_HEADER(((uintptr_t)x) & ~(HEAP_ALIGN_MASK)))
 #define GET_HEAP_SLOT(x) (GET_HEAP_HEADER(x)->base)