diff --git a/src/client/scripts/esm/chess/logic/backcompatible.js b/src/client/scripts/esm/chess/logic/backcompatible.js
index 069ce5df..10d67755 100644
--- a/src/client/scripts/esm/chess/logic/backcompatible.js
+++ b/src/client/scripts/esm/chess/logic/backcompatible.js
@@ -86,9 +86,10 @@ function getLongformatInNewNotation(longformat) {
 		//       // koth: 'both'
 		//     }
 		// }
-		const newGameRules = {};
-		newGameRules.turnOrder = turnOrder;
-		if (longformat.gameRules.slideLimit && longformat.gameRules.slideLimit !== "Infinity") newGameRules.slideLimit = longformat.gameRules.slideLimit;
+		const newGameRules = {
+			turnOrder,
+			winConditions: { white: ['checkmate'], black: ['checkmate'] }
+		};
 		if (longformat.gameRules.winConditions) {
 			const newWinConditions = { white: [], black: [] };
 			for (const condition in longformat.gameRules.winConditions) {
@@ -103,6 +104,7 @@ function getLongformatInNewNotation(longformat) {
 			// The old gamefiles did not specify promotions allowed, because it's determined by the pieces the game starts with
 			newGameRules.promotionsAllowed = variant.getPromotionsAllowed(longformat.startingPosition, newGameRules.promotionRanks);
 		}
+		if (longformat.gameRules.slideLimit && longformat.gameRules.slideLimit !== "Infinity") newGameRules.slideLimit = longformat.gameRules.slideLimit;
 		converted.gameRules = newGameRules;
 	}
 
diff --git a/src/client/scripts/esm/chess/logic/formatconverter.js b/src/client/scripts/esm/chess/logic/formatconverter.js
index 2cee2170..da97c3b5 100644
--- a/src/client/scripts/esm/chess/logic/formatconverter.js
+++ b/src/client/scripts/esm/chess/logic/formatconverter.js
@@ -308,7 +308,7 @@ function ShortToLong_Format(shortformat/*, reconstruct_optional_move_flags = tru
 		// Splice the extra gamerules out of the ICN, so that its nested [ and ] don't break the metadata parser
 		shortformat = shortformat.substring(0, indexOfGameRulesStart) + shortformat.substring(indexOfGameRulesEnd + 1, shortformat.length);
         
-		if (!isJson(stringifiedExtraGamerules)) throw new Error("Extra optional arguments not in JSON format");
+		if (!isJson(stringifiedExtraGamerules)) throw new Error(`Extra optional arguments not in valid JSON format: ${stringifiedExtraGamerules}`);
 
 		const parsedGameRules = JSON.parse(stringifiedExtraGamerules);
 		Object.assign(longformat.gameRules, parsedGameRules); // Copy over the parsed gamerules to the longformat