(CNN) South Korea's choice of dessert for Friday's historic inter-Korean summit has left a bitter taste in Japan.

Tokyo has lodged a formal protest about the mango mousse planned for the dinner between President Moon Jae-in and North Korea leader Kim Jong Un because the dish features a map of the Korean Peninsula that includes a contested island that is claimed by Japan.

Japan's Ministry of Foreign Affairs said Wednesday that Kenji Kanasugi, director-general of the Asian and Oceanian Affairs Bureau, had told the South Korean Embassy that the inclusion of Takeshima, or Dokdo island in Korean, was "very regrettable" and "not acceptable."

Japan says that South Korea is illegally occupying the rocky islands that lie east of the peninsula, and it's an issue that has long soured relations between the two countries.

South Korean Foreign Minister Kang Kyung-wha brushed off the complaint during an interview on Thursday, telling CNN's Christiane Amanpour it was a "non-issue."

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