Comms isolating transformer breaking down during hipot test

[cupoftea]

Hi,
We have an OffTheShelf signal isolating transformer in a comms setup.
The transformer and the comms driver is on the secondary side of an offline SMPS.
So we need to do a hipot test from SMPS_primary to the output of the signal transformer.
However, this always causes break down, (of the signal transformer) since the pri:sec capacitance of the signal
transformer is less than the pri:sec capacitance of the SMPS isolation transformer...so therefore most of the hipot voltage goes across pri:sec of the isolating signal
transformer.
How do you get round this?

 

[FvM]

The test is apparently exceeding signal transformer breakdown voltage. What's the use case? Either transformer rating is insufficient or test setup inappropriate.