"arity problem" on d attribute

[amapic]

Hello,
I got the "arity problem" on this code:

<animated.path
                                    d={x.to({
                                        range: [0, 1],
                                        output: [
                                            ppath,
                                            ppath2,
                                        ],
                                    })}

                                />

The exact error is :

Error: The arity of each "output" value must be equal

The 2 paths are not empty and ok. I was wondering what if the arity problem with the "d" attribute. Are the 2 paths supposed to have the same number of element, curve ... ? Thanks for your help.