Six-time champion Serena Williams overcame stern resistance from Czech 16th seed Barbora Strycova to reach the quarter-finals of the Australian Open.
The American top seed, 35, fell a break of serve down three times in the first set but came through 7-5 6-4.
Williams goes on to face Britain's Johanna Konta or Russian Ekaterina Makarova in the last eight.
"She's a really smart player - she can do pretty much everything," Williams said of Strycova.
"It was a really good match for me and I'm glad I came through it."
Williams was under pressure on serve more than usual with a first-serve percentage of just 45%.