diff --git a/usr.sbin/ctld/ctld.c b/usr.sbin/ctld/ctld.c
index 346d1908aa6..497e0f6e760 100644
--- a/usr.sbin/ctld/ctld.c
+++ b/usr.sbin/ctld/ctld.c
@@ -1568,7 +1568,7 @@ lun_set_serial(struct lun *lun, const char *value)
 }
 
 void
-lun_set_size(struct lun *lun, size_t value)
+lun_set_size(struct lun *lun, int64_t value)
 {
 
 	lun->l_size = value;
diff --git a/usr.sbin/ctld/ctld.h b/usr.sbin/ctld/ctld.h
index e1bab1a8e3b..3f4b653d689 100644
--- a/usr.sbin/ctld/ctld.h
+++ b/usr.sbin/ctld/ctld.h
@@ -349,7 +349,7 @@ void			lun_set_device_id(struct lun *lun, const char *value);
 void			lun_set_path(struct lun *lun, const char *value);
 void			lun_set_scsiname(struct lun *lun, const char *value);
 void			lun_set_serial(struct lun *lun, const char *value);
-void			lun_set_size(struct lun *lun, size_t value);
+void			lun_set_size(struct lun *lun, int64_t value);
 void			lun_set_ctl_lun(struct lun *lun, uint32_t value);
 
 struct option		*option_new(struct options *os,