diff --git a/ImperatorToCK3/CK3/Characters/CharacterCollection.cs b/ImperatorToCK3/CK3/Characters/CharacterCollection.cs
index 358d4b7fb..2732846f0 100644
--- a/ImperatorToCK3/CK3/Characters/CharacterCollection.cs
+++ b/ImperatorToCK3/CK3/Characters/CharacterCollection.cs
@@ -46,8 +46,9 @@ Configuration config
 		var parallelOptions = new ParallelOptions {
 			MaxDegreeOfParallelism = Environment.ProcessorCount - 1,
 		};
-		Parallel.ForEach(impWorld.Characters, parallelOptions, irCharacter => {
-			try {
+
+		try {
+			Parallel.ForEach(impWorld.Characters, parallelOptions, irCharacter => {
 				ImportImperatorCharacter(
 					irCharacter,
 					religionMapper,
@@ -64,11 +65,15 @@ Configuration config
 					config,
 					unlocalizedImperatorNames
 				);
-			} catch (Exception e) {
-				Logger.Error($"Exception while importing Imperator character {irCharacter.Id}: {e}");
-				Logger.Debug("Exception stack trace: " + e.StackTrace);
-			}
-		});
+			});
+		} catch (AggregateException e) {
+			var innerException = e.InnerExceptions[0];
+			Logger.Error("Exception thrown during Imperator characters import: " + innerException.Message);
+			Logger.Debug("Exception stack trace: " + innerException.StackTrace);
+			
+			// Rethrow the inner exception to stop the program.
+			throw innerException;
+		}
 		
 		if (unlocalizedImperatorNames.Any()) {
 			Logger.Warn("Found unlocalized Imperator names: " + string.Join(", ", unlocalizedImperatorNames));
diff --git a/ImperatorToCK3/CK3/Localization/CK3LocBlock.cs b/ImperatorToCK3/CK3/Localization/CK3LocBlock.cs
index 3b140ff1e..093f917db 100644
--- a/ImperatorToCK3/CK3/Localization/CK3LocBlock.cs
+++ b/ImperatorToCK3/CK3/Localization/CK3LocBlock.cs
@@ -1,12 +1,13 @@
 using commonItems.Collections;
 using commonItems.Localization;
+using System.Collections.Concurrent;
 using System.Collections.Generic;
 
 namespace ImperatorToCK3.CK3.Localization;
 
 public class CK3LocBlock : IIdentifiable<string> { // TODO: add ILocBlock interface that both this and commonItems' LocBlock would implement.
 	private readonly string baseLanguage;
-	private readonly Dictionary<string, (string, CK3LocType)> localizations = new();
+	private readonly ConcurrentDictionary<string, (string, CK3LocType)> localizations = new();
 	
 	public string Id { get; }
 	
@@ -59,7 +60,7 @@ public string? this[string language] {
 		}
 		set {
 			if (value is null) {
-				localizations.Remove(language);
+				localizations.Remove(language, out _);
 			} else {
 				localizations[language] = (value, CK3LocType.ConverterGenerated);
 			}
@@ -96,7 +97,7 @@ public void ModifyForEveryLanguage(CK3LocBlock otherBlock, TwoArgLocDelegate mod
 		foreach (var language in localizations.Keys) {
 			var locValue = modifyingFunction(localizations[language].Item1, otherBlock[language], language);
 			if (locValue is null) {
-				localizations.Remove(language);
+				localizations.Remove(language, out _);
 				continue;
 			}
 			localizations[language] = (locValue, CK3LocType.ConverterGenerated);
@@ -112,7 +113,7 @@ public void ModifyForEveryLanguage(LocDelegate modifyingFunction) {
 		foreach (var language in localizations.Keys) {
 			var locValue = modifyingFunction(localizations[language].Item1, language);
 			if (locValue is null) {
-				localizations.Remove(language);
+				localizations.Remove(language, out _);
 				continue;
 			}
 			localizations[language] = (locValue, CK3LocType.ConverterGenerated);