EJS error: include is not a function when using <%- include('partials/sidebar', { user: user, page: 'invoice' }) %>

I'm working on an Express + EJS project and getting this error when rendering my invoice.ejs view:

TypeError: C:\Users\naray\OneDrive\Desktop\Invoice-saas\invoice-generator\views\invoice.ejs:17
 >> 17|  <%- include('partials/sidebar', { user: user, page: 'invoice' }) %>
include is not a function

I’ve already installed EJS and configured it in my Express app:

app.set('view engine', 'ejs');
app.set('views', path.join(__dirname, 'views'));

My folder structure looks like this:

views/
 ├─ partials/
 │   └─ sidebar.ejs
 └─ invoice.ejs

I’m trying to include a sidebar partial and pass some variables (user, page) to it. However, EJS throws include is not a function. I’ve tried both syntaxes:

<%- include('partials/sidebar', { user: user, page: 'invoice' }) %>

and

<%- include('partials/sidebar') %>

but the error persists.

What could be causing this, and how can I properly include partials with variables in EJS?