How to pass conditionally, html boolean Attribute in heex template?

Questions / Help
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1 
<button   class="btn-step" if @account.sp_completed_at, do: "disabled"}
                    phx-click="reopen_step"
                    phx-value-step={"#{step[:name]}"}
                  >
                    Reopen
                  </button>

This used to work in eex templates. But now in heex, it throws errors Enumerable not implemented for disabled,“”, nil.Here the boolean attribute is disabled

2

https://hexdocs.pm/phoenix_live_view/Phoenix.Component.html#sigil_H/2-heex-extension-defining-attributes