eva2000 on "[Plugin: WP Super Cache] PHP Warning: Cannot use a scalar value as an array"

I'm testing out PHP 7.0.0-dev and not sure if it's related but my error log is showing the following for

Nginx 1.7.7
PHP 7.0.0-dev
WP Super Cache Version 1.4.2

FastCGI sent in stderr: "PHP message: PHP Warning: Cannot use a scalar value as an array in /../wp-settings.php on line 293" while reading response header from upstream, client:

https://wordpress.org/plugins/wp-super-cache/