Iranian authorities have arrested Pastor Youcef Nadarkhani again, this time on Christmas Day.
The pastor was acquitted of an apostasy charge in September but was told he would have to finish his three-year sentence for a different crime: evangelizing Muslims.
He served all but 45 days of that sentence and was set free after posting bail. But now Iranian authorities claim he needs to return to prison and finish his sentence.
"We are disappointed to hear Pastor Nadarkhani has been returned to prison in such an irregular manner," Mervyn Thomas, chief executive of Christian Solidarity Worldwide, said.
"The timing is insensitive and especially sad for his wife and sons, who must have been looking forward to celebrating Christmas with him for the first time in three years," Thomas added.
Christian activists worry that Nadarkhani still may not be safe, even if he is released after the 45 days are finished.
"We hope that Pastor Nadarkhani will be released without delay once this alleged sentence has been fully served," Thomas said. "We are also asking for prayers for the pastor's safety, and for his family at this difficult time."