Index: binaries/data/mods/public/simulation/components/Barter.js
===================================================================
--- binaries/data/mods/public/simulation/components/Barter.js
+++ binaries/data/mods/public/simulation/components/Barter.js
@@ -94,7 +94,7 @@
 	{
 		var amountToAdd = Math.round(prices["sell"][resourceToSell] / prices["buy"][resourceToBuy] * amount);
 		cmpPlayer.AddResource(resourceToBuy, amountToAdd);
-		var numberOfDeals = Math.round(amount / 100);
+		var numberOfDeals = Math.ceil(amount / 100);
 
 		// Display chat message to observers
 		var cmpGUIInterface = Engine.QueryInterface(SYSTEM_ENTITY, IID_GuiInterface);
Index: binaries/data/mods/public/simulation/components/tests/test_Barter.js
===================================================================
--- binaries/data/mods/public/simulation/components/tests/test_Barter.js
+++ binaries/data/mods/public/simulation/components/tests/test_Barter.js
@@ -94,12 +94,12 @@
 TS_ASSERT_EQUALS(sold, 100);
 TS_ASSERT_EQUALS(bought, Math.round(100 * (100 - cmpBarter.CONSTANT_DIFFERENCE + 0) / (100 + cmpBarter.CONSTANT_DIFFERENCE + 0)));
 
-// With an amount which is not a multiple of 100, price differences are not updated. That sounds wrong.
+// If the amount is not a multiple of 100.
 cmpBarter.priceDifferences = { "wood": 0, "stone": 0, "metal": 0 };
 cmpBarter.ExchangeResources(11, "wood", "stone", 40);
 TS_ASSERT_EQUALS(cmpBarter.restoreTimer, 7);
 TS_ASSERT(timerActivated);
-TS_ASSERT_UNEVAL_EQUALS(cmpBarter.priceDifferences, { "wood": 0, "stone": 0, "metal": 0 });
+TS_ASSERT_UNEVAL_EQUALS(cmpBarter.priceDifferences, { "wood": -cmpBarter.DIFFERENCE_PER_DEAL, "stone": cmpBarter.DIFFERENCE_PER_DEAL, "metal": 0 });
 TS_ASSERT_EQUALS(sold, 40);
 TS_ASSERT_EQUALS(bought, Math.round(40 * (100 - cmpBarter.CONSTANT_DIFFERENCE + 0) / (100 + cmpBarter.CONSTANT_DIFFERENCE + 0)));