Metal Gear Solid V: The Phantom Pain, which GameSpot recently reviewed and gave a 10, will ship on September 1 in North America and Europe, but access to its competitive multiplayer mode, Forward Operating Base, will be restricted behind a microtransaction paywall.

In The Phantom Pain, players use various resources acquired within the game to facilitate the construction of an off-shore base, but in order to participate in the online multiplayer mode, where players attack each other’s bases, they must first use real-world money to purchase MB Coins. MB Coins are then used to purchase open water in the game to make space for a PVP-dedicated base. This was discovered during GameSpot’s review process for The Phantom Pain, but without online functionality, we couldn’t determine the cost of MB Coins, or fully evaluate F.O.B. mode.

When reached for comment, Konami’s public relations team responded: “…unfortunately we don’t have any official details to share at the moment regarding the microtransaction model for F.O.B.. I should have more information for you next week though as those details are still be solidified.”

GameSpot’s review of Metal Gear Solid V: The Phantom Pain will be updated after the F.O.B. mode goes live on September 1.