diff --git a/dev/MRTCore/mrt/Microsoft.Windows.ApplicationModel.Resources/TestCommon/CommonTestCode.cs b/dev/MRTCore/mrt/Microsoft.Windows.ApplicationModel.Resources/TestCommon/CommonTestCode.cs
index ee9ce0b7c7..b5991fd3ab 100644
--- a/dev/MRTCore/mrt/Microsoft.Windows.ApplicationModel.Resources/TestCommon/CommonTestCode.cs
+++ b/dev/MRTCore/mrt/Microsoft.Windows.ApplicationModel.Resources/TestCommon/CommonTestCode.cs
@@ -5,6 +5,7 @@
 using System;
 using Microsoft.VisualStudio.TestTools.UnitTesting;
 using Microsoft.Windows.ApplicationModel.Resources;
+using Microsoft.Windows.Globalization;
 #else
 using System;
 using System.ComponentModel;
@@ -18,6 +19,7 @@
 using WEX.TestExecution;
 using WEX.TestExecution.Markup;
 using Microsoft.Windows.ApplicationModel.Resources;
+using Microsoft.Windows.Globalization;
 #endif
 
 namespace CommonTestCode
@@ -585,4 +587,23 @@ public static void NoResourceFileWithContextTest()
             Verify.IsNull(resourceCandidate);
         }
     }
+
+    public class ApplicationLanguagesTest
+    {
+        public static void PrimaryLanguageOverrideAcceptsEmptyStringTest()
+        {
+            ApplicationLanguages.PrimaryLanguageOverride = "fr-FR";
+            ApplicationLanguages.PrimaryLanguageOverride = "";
+
+            Verify.AreEqual(ApplicationLanguages.PrimaryLanguageOverride, "");
+        }
+
+        public static void PrimaryLanguageOverrideAcceptsNullStringTest()
+        {
+            ApplicationLanguages.PrimaryLanguageOverride = "fr-FR";
+            ApplicationLanguages.PrimaryLanguageOverride = null;
+
+            Verify.AreEqual(ApplicationLanguages.PrimaryLanguageOverride, ""); // C# projection of null HSTRING is empty string
+        }
+    }
 }
diff --git a/dev/MRTCore/mrt/Microsoft.Windows.ApplicationModel.Resources/src/ApplicationLanguages.cpp b/dev/MRTCore/mrt/Microsoft.Windows.ApplicationModel.Resources/src/ApplicationLanguages.cpp
index 892a3ab55a..604eebc95c 100644
--- a/dev/MRTCore/mrt/Microsoft.Windows.ApplicationModel.Resources/src/ApplicationLanguages.cpp
+++ b/dev/MRTCore/mrt/Microsoft.Windows.ApplicationModel.Resources/src/ApplicationLanguages.cpp
@@ -41,7 +41,7 @@ namespace winrt::Microsoft::Windows::Globalization::implementation
 
     void ApplicationLanguages::PrimaryLanguageOverride(hstring const& language)
     {
-        bool isValidLanguageTag = IsWellFormedTag(language.c_str());
+        bool isValidLanguageTag = language.empty() || IsWellFormedTag(language.c_str());
 
         THROW_HR_IF_MSG(E_INVALIDARG, !isValidLanguageTag, "The parameter is incorrect");
 
diff --git a/dev/MRTCore/mrt/Microsoft.Windows.ApplicationModel.Resources/unittests/UnitTest.cs b/dev/MRTCore/mrt/Microsoft.Windows.ApplicationModel.Resources/unittests/UnitTest.cs
index b234aea5a7..528a55c93f 100644
--- a/dev/MRTCore/mrt/Microsoft.Windows.ApplicationModel.Resources/unittests/UnitTest.cs
+++ b/dev/MRTCore/mrt/Microsoft.Windows.ApplicationModel.Resources/unittests/UnitTest.cs
@@ -3,6 +3,7 @@
 
 using System;
 using Microsoft.Windows.ApplicationModel.Resources;
+using Microsoft.Windows.Globalization;
 using WEX.Common.Managed;
 using WEX.Logging.Interop;
 using WEX.TestExecution;
@@ -165,4 +166,30 @@ public void NoResourceFileWithContextTest()
             CommonTestCode.ResourceContextTest.NoResourceFileWithContextTest();
         }
     }
+
+    [TestClass]
+    public class ApplicationLanguagesTest
+    {
+        [TestMethod]
+        public void PrimaryLanguageOverrideAcceptsEmptyStringTest()
+        {
+            CommonTestCode.ApplicationLanguagesTest.PrimaryLanguageOverrideAcceptsEmptyStringTest();
+        }
+
+        [TestMethod]
+        public void PrimaryLanguageOverrideAcceptsNullStringTest()
+        {
+            CommonTestCode.ApplicationLanguagesTest.PrimaryLanguageOverrideAcceptsNullStringTest();
+        }
+
+        [TestMethod]
+        public void PrimaryLanguageOverrideSetsWindowsValueTest()
+        {
+            ApplicationLanguages.PrimaryLanguageOverride = "fr-FR";
+            Verify.AreEqual(Windows.Globalization.ApplicationLanguages.PrimaryLanguageOverride, "fr-FR");
+
+            ApplicationLanguages.PrimaryLanguageOverride = null;
+            Verify.AreEqual(Windows.Globalization.ApplicationLanguages.PrimaryLanguageOverride, ""); // C# projection of null HSTRING is empty string
+        }
+    }
 }