2 files changed, 2 insertions, 2 deletions

diff --git a/src/wixext/DifxAppExtensionFactory.cs b/src/wixext/DifxAppExtensionFactory.cs
index 4565ce17..3932685d 100644
--- a/src/wixext/DifxAppExtensionFactory.cs
+++ b/src/wixext/DifxAppExtensionFactory.cs
@@ -8,7 +8,7 @@ namespace WixToolset.DifxApp
 
     public class DifxAppExtensionFactory : BaseExtensionFactory
     {
-        protected override IEnumerable<Type> ExtensionTypes => new[]
+        protected override IReadOnlyCollection<Type> ExtensionTypes => new[]
         {
             typeof(DifxAppCompiler),
             typeof(DifxAppExtensionData),
diff --git a/src/wixext/DifxAppWindowsInstallerBackendBinderExtension.cs b/src/wixext/DifxAppWindowsInstallerBackendBinderExtension.cs
index d3bbc0eb..41f01175 100644
--- a/src/wixext/DifxAppWindowsInstallerBackendBinderExtension.cs
+++ b/src/wixext/DifxAppWindowsInstallerBackendBinderExtension.cs
@@ -8,6 +8,6 @@ namespace WixToolset.DifxApp
 
     public class DifxAppWindowsInstallerBackendBinderExtension : BaseWindowsInstallerBackendBinderExtension
     {
-        public override IEnumerable<TableDefinition> TableDefinitions => DifxAppTableDefinitions.All;
+        public override IReadOnlyCollection<TableDefinition> TableDefinitions => DifxAppTableDefinitions.All;
     }
 }