diff --git a/client/windows/CCastleInterface.cpp b/client/windows/CCastleInterface.cpp
index 58e67e7b1..7655443c9 100644
--- a/client/windows/CCastleInterface.cpp
+++ b/client/windows/CCastleInterface.cpp
@@ -399,7 +399,7 @@ void CHeroGSlot::gesture(bool on, const Point & initialPosition, const Point & f
 		std::vector<std::shared_ptr<CComponent>> resComps;
 		for(TResources::nziterator i(upgradableSlots.totalCosts); i.valid(); i++)
 			resComps.push_back(std::make_shared<CComponent>(ComponentType::RESOURCE, i->resType, i->resVal));
-		if(!resComps.size())
+		if(resComps.empty())
 			resComps.push_back(std::make_shared<CComponent>(ComponentType::RESOURCE, static_cast<GameResID>(GameResID::GOLD), 0)); // add at least gold, when there are no costs
 		resComps.back()->newLine = true;
 		for(auto & upgradeInfo : upgradableSlots.upgradeInfos)