2 files changed, 3 insertions, 3 deletions

diff --git a/src/wixext/UtilExtensionFactory.cs b/src/wixext/UtilExtensionFactory.cs
index 0f87a1ff..08352813 100644
--- a/src/wixext/UtilExtensionFactory.cs
+++ b/src/wixext/UtilExtensionFactory.cs
@@ -1,4 +1,4 @@
-// Copyright (c) .NET Foundation and contributors. All rights reserved. Licensed under the Microsoft Reciprocal License. See LICENSE.TXT file in the project root for full license information.
+// Copyright (c) .NET Foundation and contributors. All rights reserved. Licensed under the Microsoft Reciprocal License. See LICENSE.TXT file in the project root for full license information.
 
 namespace WixToolset.Util
 {
@@ -8,7 +8,7 @@ namespace WixToolset.Util
 
     public class UtilExtensionFactory : BaseExtensionFactory
     {
-        protected override IEnumerable<Type> ExtensionTypes => new[]
+        protected override IReadOnlyCollection<Type> ExtensionTypes => new[]
         {
             typeof(UtilCompiler),
             typeof(UtilExtensionData),
diff --git a/src/wixext/UtilWindowsInstallerBackendExtension.cs b/src/wixext/UtilWindowsInstallerBackendExtension.cs
index f872ec1a..bca7c700 100644
--- a/src/wixext/UtilWindowsInstallerBackendExtension.cs
+++ b/src/wixext/UtilWindowsInstallerBackendExtension.cs
@@ -8,6 +8,6 @@ namespace WixToolset.Util
 
     public class UtilWindowsInstallerBackendBinderExtension : BaseWindowsInstallerBackendBinderExtension
     {
-        public override IEnumerable<TableDefinition> TableDefinitions => UtilTableDefinitions.All;
+        public override IReadOnlyCollection<TableDefinition> TableDefinitions => UtilTableDefinitions.All;
     }
 }