It's polite, of course, to congratulate the new leader of a neighbour and ally.
But the tone of EU leaders' messages to Liz Truss - seen here in Brussels as a hardliner on Brexit, and a hawk when it comes to Russia - reveals a lot more than a superficial "well done".
Ursula von der Leyen, the European Commission chief, tweeted that the UK and EU were partners, facing current challenges together - but that she hoped as prime minister, Liz Truss would be "constructive", respecting agreements previously reached between the two sides.
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MEP Nathalie Loiseau, France's former Europe minister, was more direct, tweeting: "I hope she will refrain from making things more difficult between the EU and the UK."
Politicians in Eastern Europe, meanwhile, who openly applaud the UK for its tough stance towards the Kremlin, were unreservedly warm.
Estonia's Prime Minister Kaja Kallas tweeted a photo of her alongside Liz Truss during her time as British foreign secretary, saying: "I'm confident our partnership will only grow."