Petr Cech's goalkeeping gloves were mistakenly sent to Chelsea's training ground this week.
The Czech Republic international left the Blues to join Arsenal in the summer but his glove sponsor adidas must have forgotten when sending him a custom-made set ahead of this weekend's clash between the two London clubs.
Cech's gloves were sent to the Cobham training centre in Surrey before the Blues kindly forwarded them to Arsenal's Colney base in Hertfordshire.
A Chelsea source told the Daily Mirror: "The glove manufacturers obviously still think of Petr Cech as part of the furniture at Chelsea.
"It's strange to think of him at another club."