Enbridge Inc, Canada’s largest pipeline operator, said on Friday it would buy its U.S. master limited partnership Spectra Energy Partners for a sweetened deal of $3.3 billion.

Pipeline companies are reorganizing their business structure after the U.S. Federal Energy Regulatory Commission in March stopped them from claiming an income tax allowance as part of the fees they charge shippers.

“Significant weakening of the US Master Limited Partnership capital markets has adversely affected the growth opportunities for MLPs, including Spectra,” Enbridge said in a statement.

Enbridge raised its offer to 1.111 of its common shares for each Spectra unit, compared with its previous offer of 1.0123 of its shares.

Spectra Energy shares rose 5.7 percent to $40 in premarket trading, while those of Enbridge were marginally down.