diff --git a/src/tools/illink/test/Mono.Linker.Tests.Cases/DataFlow/NullableAnnotations.cs b/src/tools/illink/test/Mono.Linker.Tests.Cases/DataFlow/NullableAnnotations.cs
index 8f11a98281eee7..29b8bf650cbffa 100644
--- a/src/tools/illink/test/Mono.Linker.Tests.Cases/DataFlow/NullableAnnotations.cs
+++ b/src/tools/illink/test/Mono.Linker.Tests.Cases/DataFlow/NullableAnnotations.cs
@@ -65,6 +65,9 @@ public static void Main ()
 			GetUnderlyingTypeOnNonNullableKnownType.Test ();
 			MakeGenericTypeWithUnknownValue (new object[2] { 1, 2 });
 			MakeGenericTypeWithKnowAndUnknownArray ();
+
+			// Prevents optimizing away 'as Type' conversion.
+			PreserveSystemType ();
 		}
 
 		[Kept]
@@ -331,5 +334,11 @@ static void MakeGenericTypeWithKnowAndUnknownArray (Type[] unknownTypes = null,
 			nullable.GetProperties ();   // This works - we still know it's Nullable<>, so we can get its properties
 			Nullable.GetUnderlyingType (nullable).GetFields (); // This must warn - since we have no idea what the underlying type is for the unknownTypes case
 		}
+
+		[Kept]
+		static void PreserveSystemType ()
+		{
+			typeof (Type).RequiresNonPublicConstructors ();
+		}
 	}
 }
diff --git a/src/tools/illink/test/Mono.Linker.Tests.Cases/UnreachableBlock/ComplexConditions.cs b/src/tools/illink/test/Mono.Linker.Tests.Cases/UnreachableBlock/ComplexConditions.cs
index 68714608fcca98..4d2838c3b9ebfe 100644
--- a/src/tools/illink/test/Mono.Linker.Tests.Cases/UnreachableBlock/ComplexConditions.cs
+++ b/src/tools/illink/test/Mono.Linker.Tests.Cases/UnreachableBlock/ComplexConditions.cs
@@ -1,6 +1,7 @@
 using System;
 using System.Reflection.Emit;
 using Mono.Linker.Tests.Cases.Expectations.Assertions;
+using Mono.Linker.Tests.Cases.Expectations.Helpers;
 using Mono.Linker.Tests.Cases.Expectations.Metadata;
 
 namespace Mono.Linker.Tests.Cases.UnreachableBlock
@@ -14,6 +15,9 @@ public static void Main ()
 		{
 			Test_1 (null);
 			Test_2 (9);
+
+			// Prevents optimizing away 'is Type' check.
+			PreserveSystemType ();
 		}
 
 		[Kept]
@@ -100,5 +104,11 @@ static bool IsDynamicCodeSupported {
 		static void Reached_1 ()
 		{
 		}
+
+		[Kept]
+		static void PreserveSystemType ()
+		{
+			typeof (Type).RequiresNonPublicConstructors ();
+		}
 	}
 }
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