1 files changed, 8 insertions, 1 deletions
diff --git a/file.c b/file.c
index e6fe603a1d..3b52c900a1 100644
--- a/file.c
+++ b/file.c
@@ -4147,10 +4147,16 @@ static VALUE
 rb_file_truncate(VALUE obj, VALUE len)
 {
     rb_io_t *fptr;
+#if defined(HAVE_FTRUNCATE)
+#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);
     GetOpenFile(obj, fptr);
     if (!(fptr->mode & FMODE_WRITABLE)) {
 	rb_raise(rb_eIOError, "not opened for writing");
@@ -4164,6 +4170,7 @@ rb_file_truncate(VALUE obj, VALUE len)
 	rb_sys_fail_path(fptr->pathv);
 #endif
     return INT2FIX(0);
+#undef NUM2POS
 }
 #else
 #define rb_file_truncate rb_f_notimplement