Finite size effect in the specific heat of YBa2Cu3O7-delta

We analyze high precision, high resolution microcalorimetric specific heat data of detwinned YBa2Cu3O(7-delta) single crystals. It is shown that a finite size effect must be taken into account when attempting to extract critical properties. Contrary to previous claims, there is no contradiction to a regular second order phase transition. Consistency with 3D-XY critical behavior is demonstrated.