diff --git a/ImperatorToCK3/Imperator/Provinces/ProvinceCollection.cs b/ImperatorToCK3/Imperator/Provinces/ProvinceCollection.cs
index fa60bf781..51c1c65f9 100644
--- a/ImperatorToCK3/Imperator/Provinces/ProvinceCollection.cs
+++ b/ImperatorToCK3/Imperator/Provinces/ProvinceCollection.cs
@@ -63,7 +63,7 @@ private void DetermineImpassableOwnership(MapData irMapData) {
 
 		// Group the neighboring provinces by their owner. The one with most owned neighbors may be the owner of the impassable.
 		var ownerCandidate = neighborProvIds
-			.Select(provId => this[provId].OwnerCountry)
+			.Select(provId => TryGetValue(provId, out var prov) ? prov.OwnerCountry : null)
 			.Where(country => country is not null)
 			.GroupBy(country => country)
 			.OrderByDescending(group => group.Count())