dotnet
diff --git a/‎src/libraries/System.Collections/tests/Generic/Dictionary/Dictionary.Tests.cs‎
Lines changed: 16 additions & 0 deletions b/‎src/libraries/System.Collections/tests/Generic/Dictionary/Dictionary.Tests.cs‎
Lines changed: 16 additions & 0 deletions
@@ -337,6 +337,22 @@ public void CantAcceptDuplicateKeysFromSourceDictionary()
             AssertExtensions.Throws<ArgumentException>(null, () => new Dictionary<string, int>(source, StringComparer.OrdinalIgnoreCase));
         }
 
+        [ConditionalFact(typeof(PlatformDetection), nameof(PlatformDetection.IsNotInvariantGlobalization))]
+        // https://github.com/dotnet/runtime/issues/44681
+        public void DictionaryOrdinalIgnoreCaseCyrillicKeys()
+        {
+            const string Lower = "абвгдеёжзийклмнопрстуфхцчшщьыъэюя";
+            const string Higher = "АБВГДЕЁЖЗИЙКЛМНОПРСТУФХЦЧШЩЬЫЪЭЮЯ";
+
+            var dictionary = new Dictionary<string, int>(StringComparer.OrdinalIgnoreCase);
+
+            for (int i = 0; i < Lower.Length; i++)
+            {
+                dictionary[Lower[i].ToString()] = i;
+                Assert.Equal(i, dictionary[Higher[i].ToString()]);
+            }
+        }
+
         public static IEnumerable<object[]> CopyConstructorStringComparerData
         {
             get