diff --git a/ChangeLog b/ChangeLog
index b1d31827de..2abf0bff24 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,7 @@
+Sat Jun  8 06:15:46 2013  Tanaka Akira  <akr@fsij.org>
+
+	* random.c (numberof): Removed.
+
 Sat Jun  8 06:00:47 2013  Tanaka Akira  <akr@fsij.org>
 
 	* random.c: include internal.h.
diff --git a/random.c b/random.c
index 4b43773cac..98332c00b8 100644
--- a/random.c
+++ b/random.c
@@ -271,7 +271,6 @@ rb_genrand_real(void)
 #define BDIGMAX ((BDIGIT)-1)
 
 #define roomof(n, m) (int)(((n)+(m)-1) / (m))
-#define numberof(array) (int)(sizeof(array) / sizeof((array)[0]))
 #define SIZEOF_INT32 (31/CHAR_BIT + 1)
 
 static double