Test series between England and South Africa will comprise five matches after the International Cricket Council granted the clashes 'icon' status.
The next series after the current four-Test battle, in South Africa in 2009-10, will include an extra match.
The England and Wales Cricket Board (ECB) had lobbied for the change.
"ECB welcomes the invitation to play five Test matches and three one-day internationals on our next tour," said ECB chief executive David Collier.
The teams' current four-test series in England is level after the first match at Lord's ended in a draw on Monday.
Of the six series between the two countries since South Africa's readmission to world cricket following the end of its apartheid system, each side has won two and the other two have been drawn.
Cricket South Africa had also called for the expansion, which has now been ratified.
Collier added: "ECB has consistently stated that Test matches are the pinnacle of world cricket and this agreement demonstrates our commitment to that principle."
ICC chief executive Haroon Lorgat added: "ICC warmly welcomes this accord between the ECB and Cricket South Africa.
"Test cricket remains the supreme test of individual players and teams."
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