[Rails] undefined method `stringify_keys' for #

From my understanding, you can pass a block to the link_to helper, but
the following code gives me an error "undefined method
`stringify_keys' for #<String:0x007fe8a3ba0a48>".

= link_to("One time Payment with Paypal or Credit Card",
@order.payment_payment_standard_url(new_order_url(invoice: @invoice),
payment_notifications_url, @invoice)) do
= image_tag "https://www.paypalobjects.com/webstatic/
mktg/logo/AM_mc_vs_dc_ae.jpg"

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