Open Text Corp. has topped a bid from a U.S. firm to buy software company Hummingbird Ltd.

Based in Waterloo, Ont., Open Text said it is offering $27.75 US per share for Hummingbird, making its takeover bid worth about $482.9 million US.

On May 26, Toronto-based Hummingbird Ltd.'s board of directors said it had approved a $465-million US deal to sell the business software company to California-based Symphony Technology Group. Symphony is offering $26.75 US per share for Hummingbird.

"We believe this acquisition will benefit the shareholders, customers, partners and employees of both companies," said John Shackleton, Open Text's president and CEO.

"Open Text believes that its offer is at an attractive premium and price to Hummingbird shareholders," he said in a release.

Itself a software developer, Open Text said it already owns 4.3 per cent of Hummingbird's common shares, andshareholders who own about 18 per cent of Hummingbird's shares have agreed to tender their holdingsto the Open Text offer.

In the wake of the latest offer, Hummingbird shares were up more than4 per cent on the TSX, rising $1.25 to $31.74. Open Text was off62 cents at $15.07.