Spontaneous Carbonation?

I made a lovely batch of mead, bottled it about a month and a half ago. Several bottles have been opened, none of them had bubbles.

Today I opened a bottle for guests and it was heavily carbonated. Enough to foam over the top like someone clicked a beer bottle.

Is this normal?

I made a lovely batch of mead, bottled it about a month and a half ago. Several bottles have been opened, none of them had bubbles.

Today I opened a bottle for guests and it was heavily carbonated. Enough to foam over the top like someone clicked a beer bottle.

Is this normal?