diff --git a/ChangeLog b/ChangeLog
index 84f4dcd4ef..13f8efe144 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,10 @@
+Sun May 12 17:25:46 2013  KOSAKI Motohiro  <kosaki.motohiro@gmail.com>
+
+	* configure.in: removes AC_CHECK_FUNCS(truncate64) because it's
+	  unused.
+	* file.c (rb_file_s_truncate): use correct type. chsize takes
+	  a long.
+
 Sun May 12 17:18:46 2013  KOSAKI Motohiro  <kosaki.motohiro@gmail.com>
 
 	* process.c: move '#define SPAWNV 1' to win32/Makefile.sub.
diff --git a/configure.in b/configure.in
index 8c8daa8703..09a29b0742 100644
--- a/configure.in
+++ b/configure.in
@@ -1810,7 +1810,7 @@ AC_CHECK_FUNCS(telldir)
 AC_CHECK_FUNCS(timegm)
 AC_CHECK_FUNCS(times)
 AC_CHECK_FUNCS(truncate)
-AC_CHECK_FUNCS(truncate64)
+AC_CHECK_FUNCS(truncate64)		# used for Win32
 AC_CHECK_FUNCS(unsetenv)
 AC_CHECK_FUNCS(utimensat)
 AC_CHECK_FUNCS(utimes)
diff --git a/file.c b/file.c
index 3b52c900a1..9b6ae64ae1 100644
--- a/file.c
+++ b/file.c
@@ -4098,10 +4098,16 @@ rb_file_s_join(VALUE klass, VALUE args)
 static VALUE
 rb_file_s_truncate(VALUE klass, VALUE path, VALUE len)
 {
+#ifdef HAVE_TRUNCATE
+#define NUM2POS(n) NUM2OFFT(n)
     off_t pos;
+#else
+#define NUM2POS(n) NUM2LONG(n)
+    long pos;
+#endif
 
     rb_secure(2);
-    pos = NUM2OFFT(len);
+    pos = NUM2POS(len);
     FilePathValue(path);
     path = rb_str_encode_ospath(path);
 #ifdef HAVE_TRUNCATE
@@ -4123,6 +4129,7 @@ rb_file_s_truncate(VALUE klass, VALUE path, VALUE len)
     }
 #endif
     return INT2FIX(0);
+#undef NUM2POS
 }
 #else
 #define rb_file_s_truncate rb_f_notimplement