diff --git a/src/libraries/System.Text.Json/tests/System.Text.Json.Tests/Serialization/PolymorphicTests.TypeClassifier.cs b/src/libraries/System.Text.Json/tests/System.Text.Json.Tests/Serialization/PolymorphicTests.TypeClassifier.cs
index b8b7f26243f291..2763d73d06d6ab 100644
--- a/src/libraries/System.Text.Json/tests/System.Text.Json.Tests/Serialization/PolymorphicTests.TypeClassifier.cs
+++ b/src/libraries/System.Text.Json/tests/System.Text.Json.Tests/Serialization/PolymorphicTests.TypeClassifier.cs
@@ -741,7 +741,6 @@ public void MetadataServices_NullPolymorphismOptions_ReadsAttributes()
         }
 
         [Fact]
-        [ActiveIssue("https://github.com/dotnet/runtime/issues/128765", typeof(PlatformDetection), nameof(PlatformDetection.IsAppleMobile), nameof(PlatformDetection.IsMonoRuntime))]
         public void MetadataServices_NullPolymorphismOptions_DoesNotActivateAttributeClassifier()
         {
             JsonTypeInfo<AttrClassifiedAnimal> typeInfo = JsonMetadataServices.CreateObjectInfo(
@@ -752,18 +751,9 @@ public void MetadataServices_NullPolymorphismOptions_DoesNotActivateAttributeCla
                 });
 
             JsonPolymorphismOptions options = Assert.IsType<JsonPolymorphismOptions>(typeInfo.PolymorphismOptions);
-            Assert.Collection(
-                options.DerivedTypes,
-                derivedType =>
-                {
-                    Assert.Equal(typeof(AttrClassifiedDog), derivedType.DerivedType);
-                    Assert.Equal("dog", derivedType.TypeDiscriminator);
-                },
-                derivedType =>
-                {
-                    Assert.Equal(typeof(AttrClassifiedCat), derivedType.DerivedType);
-                    Assert.Equal("cat", derivedType.TypeDiscriminator);
-                });
+            Assert.Equal(2, options.DerivedTypes.Count);
+            Assert.Contains(options.DerivedTypes, dt => dt.DerivedType == typeof(AttrClassifiedDog) && Equals("dog", dt.TypeDiscriminator));
+            Assert.Contains(options.DerivedTypes, dt => dt.DerivedType == typeof(AttrClassifiedCat) && Equals("cat", dt.TypeDiscriminator));
 
             Assert.Null(typeInfo.TypeClassifier);
         }