Breaking the fast prior to sunset by mistake

Q: What does the Shari'ah say about a person who mistakenly breaks his fast before sunset?

A: If in spite of having taken all precautions, a person mistakenly breaks his fast before the correct time under the impression that the sun has already set while it is not the case, then there is no blame on him nor is there any Kaffaarah, but he will have to replace that fast.

[English version of "Faire iftaar par erreur avant soleil couché" Al Jamiat Vol.1 No.4]