{% compatibility true, '3.5.0', null, '3.5.0', 'Argument type' %}
In older versions of LibSass and Ruby Sass, the [`call()` function][] took a
string representing a function's name. This was changed to take a function
value instead in preparation for a new module system where functions are no
longer global and so a given name may not always refer to the same function.

[`call()` function]: /documentation/modules/meta#call

Passing a string to `call()` still works in all implementations, but it's
deprecated and will be disallowed in future versions.
{% endcompatibility %}