diff --git a/src/models/blogs.rs b/src/models/blogs.rs
index 8bf31d65..7dfe5705 100644
--- a/src/models/blogs.rs
+++ b/src/models/blogs.rs
@@ -34,14 +34,6 @@ impl Blog {
             .expect("Error saving new blog")
     }
 
-    pub fn compute_outbox(blog: String, hostname: String) -> String {
-        format!("https://{}/~/{}/outbox", hostname, blog)
-    }
-
-    pub fn compute_inbox(blog: String, hostname: String) -> String {
-        format!("https://{}/~/{}/inbox", hostname, blog)
-    }
-
     pub fn get(conn: &PgConnection, id: i32) -> Option<Blog> {
         blogs::table.filter(blogs::id.eq(id))
             .limit(1)
@@ -57,6 +49,20 @@ impl Blog {
             .expect("Error loading blog by email")
             .into_iter().nth(0)
     }
+
+    pub fn update_boxes(&self, conn: &PgConnection) {
+        if self.outbox_url.len() == 0 {
+            diesel::update(self)
+                .set(blogs::outbox_url.eq(self.compute_outbox(conn)))
+                .get_result::<Blog>(conn).expect("Couldn't update outbox URL");
+        }
+
+        if self.inbox_url.len() == 0 {
+            diesel::update(self)
+                .set(blogs::inbox_url.eq(self.compute_inbox(conn)))
+                .get_result::<Blog>(conn).expect("Couldn't update inbox URL");
+        }
+    }
 }
 
 impl Actor for Blog {
@@ -72,3 +78,21 @@ impl Actor for Blog {
         Instance::get(conn, self.instance_id).unwrap()
     }
 }
+
+impl NewBlog {
+    pub fn new_local(
+        actor_id: String,
+        title: String,
+        summary: String,
+        instance_id: i32
+    ) -> NewBlog {
+        NewBlog {
+            actor_id: actor_id,
+            title: title,
+            summary: summary,
+            outbox_url: String::from(""),
+            inbox_url: String::from(""),
+            instance_id: instance_id
+        }
+    }
+}
diff --git a/src/models/user.rs b/src/models/user.rs
index 4d9afe1c..681dae36 100644
--- a/src/models/user.rs
+++ b/src/models/user.rs
@@ -49,14 +49,6 @@ impl User {
             .expect("Error saving new user")
     }
 
-    pub fn compute_outbox(user: String, hostname: String) -> String {
-        format!("https://{}/@/{}/outbox", hostname, user)
-    }
-
-    pub fn compute_inbox(user: String, hostname: String) -> String {
-        format!("https://{}/@/{}/inbox", hostname, user)
-    }
-
     pub fn get(conn: &PgConnection, id: i32) -> Option<User> {
         users::table.filter(users::id.eq(id))
             .limit(1)
@@ -88,6 +80,20 @@ impl User {
     pub fn auth(&self, pass: String) -> bool {
         bcrypt::verify(pass.as_str(), self.hashed_password.clone().unwrap().as_str()).is_ok()
     }
+
+    pub fn update_boxes(&self, conn: &PgConnection) {
+        if self.outbox_url.len() == 0 {
+            diesel::update(self)
+                .set(users::outbox_url.eq(self.compute_outbox(conn)))
+                .get_result::<User>(conn).expect("Couldn't update outbox URL");                
+        }
+
+        if self.inbox_url.len() == 0 {
+            diesel::update(self)
+                .set(users::inbox_url.eq(self.compute_inbox(conn)))
+                .get_result::<User>(conn).expect("Couldn't update outbox URL");                
+        }
+    }
 }
 
 impl<'a, 'r> FromRequest<'a, 'r> for User {
@@ -116,3 +122,28 @@ impl Actor for User {
         Instance::get(conn, self.instance_id).unwrap()
     }
 }
+
+impl NewUser {
+    /// Creates a new local user
+    pub fn new_local(
+        username: String,
+        display_name: String,
+        is_admin: bool,
+        summary: String,
+        email: String,
+        password: String,
+        instance_id: i32
+    ) -> NewUser {
+        NewUser {
+            username: username,
+            display_name: display_name,
+            outbox_url: String::from(""),
+            inbox_url: String::from(""),
+            is_admin: is_admin,
+            summary: summary,
+            email: Some(email),
+            hashed_password: Some(password),
+            instance_id: instance_id
+        }
+    }
+}
diff --git a/src/routes/blogs.rs b/src/routes/blogs.rs
index 9ddc6221..a6d42e7c 100644
--- a/src/routes/blogs.rs
+++ b/src/routes/blogs.rs
@@ -30,14 +30,12 @@ fn create(conn: DbConn, data: Form<NewBlogForm>, _user: User) -> Redirect {
     let form = data.get();
     let slug = utils::make_actor_id(form.title.to_string());
 
-    Blog::insert(&*conn, NewBlog {
-        actor_id: slug.to_string(),
-        title: form.title.to_string(),
-        summary: String::from(""),
-        outbox_url: Blog::compute_outbox(slug.to_string(), inst.public_domain.to_string()),
-        inbox_url: Blog::compute_inbox(slug.to_string(), inst.public_domain.to_string()),
-        instance_id: inst.id
-    });
+    Blog::insert(&*conn, NewBlog::new_local(
+        slug.to_string(),
+        form.title.to_string(),
+        String::from(""),
+        inst.id
+    )).update_boxes(&*conn);
     
     Redirect::to(format!("/~/{}", slug).as_str())
 }
diff --git a/src/routes/user.rs b/src/routes/user.rs
index a328fdea..1cc3a097 100644
--- a/src/routes/user.rs
+++ b/src/routes/user.rs
@@ -6,6 +6,7 @@ use std::collections::HashMap;
 use db_conn::DbConn;
 use models::user::*;
 use models::instance::Instance;
+use activity_pub::Actor;
 
 #[get("/me")]
 fn me(user: User) -> String {
@@ -36,17 +37,15 @@ fn create(conn: DbConn, data: Form<NewUserForm>) -> Redirect {
     let form = data.get();
 
     if form.password == form.password_confirmation {
-        User::insert(&*conn, NewUser {
-            username: form.username.to_string(),
-            display_name: form.username.to_string(),
-            outbox_url: User::compute_outbox(form.username.to_string(), inst.public_domain.to_string()),
-            inbox_url: User::compute_inbox(form.username.to_string(), inst.public_domain.to_string()),
-            is_admin: !inst.has_admin(&*conn),
-            summary: String::from(""),
-            email: Some(form.email.to_string()),
-            hashed_password: Some(User::hash_pass(form.password.to_string())),
-            instance_id: inst.id
-        });
+        User::insert(&*conn, NewUser::new_local(
+            form.username.to_string(),
+            form.username.to_string(),
+            !inst.has_admin(&*conn),
+            String::from(""),
+            form.email.to_string(),
+            User::hash_pass(form.password.to_string()),
+            inst.id
+        )).update_boxes(&*conn);
     }
     
     Redirect::to(format!("/@/{}", data.get().username).as_str())