Warning type err will be better

[gshmu]

Error running 'serve': class java.lang.Integer cannot be cast to class java.lang.String (java.lang.Integer and java.lang.String are in module java.base of loader 'bootstrap')

Error running 'serve': class java.lang.Boolean cannot be cast to class java.lang.String (java.lang.Boolean and java.lang.String are in module java.base of loader 'bootstrap')

The Unix ENV master be string, but I think convert the var to string and add warning will be better.

[ashald]

I'm not sure I understand. Could you clarify?