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Bride-to-be Meghan Markle has invited her former co-stars from TV show "Suits," but it has been revealed some of the actors are unsure how to dress for a royal wedding.

The stars have turned to shows’ wardrobe department amid fears they’ll get the dress code wrong, the Express claimed.

The show’s actors who scored an invite to the wedding have chosen to use the same team who dress them for the TV legal drama to prepare their outfits for the May 19 royal wedding.

An insider said they had struggled with the dress code of “dress uniform, morning coat or lounge suit."

They added: “Two outfits are required for the May festivities, with the men asked to wear a morning suit, which, a few invitees have learned, isn’t particularly easy to secure stateside.”

Another source said: “All the main cast members are going I think and a few of the crew.

markle suits costars nbc

Pictured: (l-r) Meghan Markle as Rachel Zane, Patrick J. Adams as Mike Ross in an episode of "Suits." (NBC)

“There’s a real hustle and bustle of excitement on the set of the show in Toronto with people getting their outfits made.

“Last time I was there, I happened to run into a couple of people in wardrobe who were helping getting things made for some of those that are going.

“They were just helping with some of the ladies outfits, helping with the dresses and the hats.”

The insider also said the men will be wearing “morning suits”.

“I think it’s just a couple of people they are helping with it. I don’t think they’re making the men’s clothing, I think they will be wearing morning suits.

“I understand everyone is to wear a hat of some kind, there are a couple of choices ... whatever they wear in England, they wear those little side hats.”

Prince Harry and Meghan Markle will marry at St George’s Chapel, with many A-listers are expected to attend.

Markle’s former co-stars are all believed to be attending.

Markle is close with her on-screen love interest Patrick J. Adams and co-star Abigail Spencer.

The source continued: “A lot of the crew is Canadian and they live in Toronto and a few of them are going.

“I think those really invested in the show will be there.

“They are very good, they’re extremely good, you can look at Sarah’s clothing and Gina’s clothing and see how wonderful they are.

“They just do it all.”

It is reported that executives at the show have cleared shooting schedules for the wedding.

This article originally appeared on News.com.au.