# general


05/13/2019, 11:12 AM
I'm having a strange issue trying to use express js in a lambda. It's to do with how error handlers are called. The way express distinguishes between an error handler and a non-error handler is by checking the function.length which returns the arity of the function. It seems somewhere between the source code and what's getting deployed something is messing with this as an arity of 0 is logged out. Are there any known issues around this? Could pulumi's serialization be breaking it?