Jake Bidwell has had his loan spell at Brentford extended until 5 January.
The Everton left-back joined the Bees on an intial one-month deal in August after a successful six month spell with Uwe Rösler's side last term.
One-month extensions were then agreed in September and October - and this latest development will see the 19-year-old continue with the League One outfit into the New Year.
Blues boss David Moyes is pleased with the progress the teenager is making and was more than happy to let him remain with the Londoners.
He said: “We're delighted with Jake being there.
"He's at a good club and really enjoyed his first spell - we sent Adam Forshaw there who was the same.
“It's good for Jake to get league football. He's a great boy, committed, diligent in his work and I think at the moment it's a good stepping stone for him.”
Bidwell has made 16 starts and one substitute appearance for the Bees, who currently lie just outside the play-off places.