The Toronto Stock Exchange has halted trading in shares of BCE Inc. until further notice.

The exchange says “a trading message protocol issue this morning caused a service interruption in trading for approximately 45 minutes.”

“This issue has created some data integrity concerns and therefore the decision has been to halt trading in this issue.”

Shares of BCE tumbled in very heavy trading Thursday after a court ruling threw into question the biggest takeover in Canadian history.

BCE stocks opened at $31.99, down $5.13 from Wednesday’s close.

Late Wednesday, the Quebec Court of Appeal overturned a lower court decision and siding with Bell bondholders who’d complained that the takeover treated them unfairly.

The bondholders had argued that the leveraged buyout would saddle the company with so much new debt that the value of their bonds would drop.