diff --git a/CHANGELOG.md b/CHANGELOG.md
index 895773a..22b8916 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -31,6 +31,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 - [L10NSharp] Removed emailForSubmissions parameter from LocalizationManager.Create. Since the localization dialog was jettisoned, it no longer makes sense to store this information on the localization manager.
 - [L10NSharp.Windows.Forms] Removed emailForSubmissions parameter (8th parameter) from LocalizationManagerWinforms.Create. Since the localization dialog was jettisoned, it no longer makes sense to store this information on the localization manager.
 - [L10NSharp] Replaced the .NET 8.0 target with .NET Standard 2.0 for broader compatibility.
+- [L10NSharp] BREAKING CHANGE: `LocalizationManager.GetString`, `GetDynamicString`, and `GetDynamicStringOrEnglish` now throw `ArgumentException` when called with a null or empty string ID. Previously, empty IDs were silently accepted and could produce a malformed XLIFF file that crashed on next launch. (#104)
  
 ### Fixed
 
diff --git a/src/L10NSharp.Tests/LocalizationManagerTestsBase.cs b/src/L10NSharp.Tests/LocalizationManagerTestsBase.cs
index 5189f53..9949eff 100644
--- a/src/L10NSharp.Tests/LocalizationManagerTestsBase.cs
+++ b/src/L10NSharp.Tests/LocalizationManagerTestsBase.cs
@@ -292,6 +292,20 @@ public void GetDynamicStringInEnglish_NoDefault_FindsEnglish()
 			}
 		}
 
+		[Test]
+		public void GetDynamicString_WithEmptyId_ThrowsArgumentException()
+		{
+			Assert.Throws<ArgumentException>(() =>
+				LocalizationManager.GetDynamicString(AppId, "", "some text"));
+		}
+
+		[Test]
+		public void GetDynamicStringOrEnglish_WithEmptyId_ThrowsArgumentException()
+		{
+			Assert.Throws<ArgumentException>(() =>
+				LocalizationManagerInternal<T>.GetDynamicStringOrEnglish(AppId, "", "some text", null, "en"));
+		}
+
 		[Test]
 		public void GetDynamicStringOrEnglish_LmDisposed_GivesUsefulException()
 		{
diff --git a/src/L10NSharp/LocalizationManagerInternal.cs b/src/L10NSharp/LocalizationManagerInternal.cs
index e8ecef8..e3996ed 100644
--- a/src/L10NSharp/LocalizationManagerInternal.cs
+++ b/src/L10NSharp/LocalizationManagerInternal.cs
@@ -464,6 +464,8 @@ public static string GetDynamicString(string appId, string id, string englishTex
 		/// ------------------------------------------------------------------------------------
 		public static string GetDynamicString(string appId, string id, string englishText, string comment)
 		{
+			if (string.IsNullOrWhiteSpace(id))
+				throw new ArgumentException("id may not be null or empty.", nameof(id));
 			return GetDynamicStringOrEnglish(appId, id, englishText, comment, LocalizationManager.UILanguageId);
 		}
 
@@ -482,6 +484,8 @@ public static string GetDynamicString(string appId, string id, string englishTex
 		public static string GetDynamicStringOrEnglish(string appId, string id, string englishText,
 			string comment, string langId)
 		{
+			if (string.IsNullOrWhiteSpace(id))
+				throw new ArgumentException("id may not be null or empty.", nameof(id));
 			// This happens in unit test environments or apps that have imported a library that
 			// is localized, but the app itself isn't initializing L10N yet.
 			if (LoadedManagers.Count == 0)
diff --git a/src/L10NSharp/XLiffUtils/XliffTransUnitUpdater.cs b/src/L10NSharp/XLiffUtils/XliffTransUnitUpdater.cs
index 6d9cd27..c8a028c 100644
--- a/src/L10NSharp/XLiffUtils/XliffTransUnitUpdater.cs
+++ b/src/L10NSharp/XLiffUtils/XliffTransUnitUpdater.cs
@@ -46,6 +46,8 @@ internal bool Update(LocalizingInfo locInfo)
 			// Can't do anything without a language id.
 			if (string.IsNullOrEmpty(locInfo.LangId))
 				return _updated;
+			if (string.IsNullOrEmpty(locInfo.Id))
+				return _updated;
 
 			var xliffSource = _stringCache.GetDocument(_defaultLang);
 			Debug.Assert(xliffSource != null);