A WT extension looks like

extensions=[local={entry=functionName,early_load=true,config={key="value"}},]

Previously the config string passed in was:

{entry=functionName,early_load=true,config={key="value"}}

However now, only the "config" piece is passed in:

{key="value"}

The code is still trying to parse the "config" value out of the string which results in an error and failure to start up.