diff --git a/ChangeLog b/ChangeLog
index 23f993c04c..35f4be3d0c 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,7 @@
+Sat Mar  6 22:07:09 2010  Tanaka Akira  <akr@fsij.org>
+
+	* pack.c: fix the prototype of rb_big2ulong_pack.
+
 Sat Mar  6 13:45:37 2010  Yusuke Endoh  <mame@tsg.ne.jp>
 
 	* io.c (rb_io_s_write, rb_io_s_binwrite): delete File#write and
diff --git a/pack.c b/pack.c
index c3346a4b71..0a551f6881 100644
--- a/pack.c
+++ b/pack.c
@@ -266,7 +266,7 @@ TOKEN_PASTE(swap,x)(xtype z)		\
 # define VTOHD(x,y)	rb_vtohd(x)
 #endif
 
-unsigned long rb_big2ulong_pack(VALUE x);
+VALUE rb_big2ulong_pack(VALUE x);
 
 static unsigned long
 num2i32(VALUE x)