One who drinks after the dawn while believing the night is still there

Question: On a day in Ramadan, I intended to fast. After that, I dozed off and woke up to hear the news on the radio. I thought the call to Fajr had not been made yet, so I drank some water. I later realized that the call to Fajr had already been made. Does this invalidate my fast?

Answer: Yes, you must make up the fast; because you ate intentionally, not out of forgetfulness, after the dawn had appeared.