Defilement or corruption?

There is a hymn that we sing quite frequently:

More honourable than the Cherubim

And more glorious beyond compare than the Seraphim

Without defilement you gave birth to God the Word

True Theotokos we magnify you.

Recently our choir has begun to sing "without corruption you gave birth to God the Word", which seems decidedly odd.

The change was not explained at all, and apparently the parish priest was not consulted about it, but I gather that similar changes have taken place in a number of...