diff --git a/src/AppMotor.Core/Extensions/TypeExtensions.cs b/src/AppMotor.Core/Extensions/TypeExtensions.cs
index 76f6e2f7..9cb05bc5 100644
--- a/src/AppMotor.Core/Extensions/TypeExtensions.cs
+++ b/src/AppMotor.Core/Extensions/TypeExtensions.cs
@@ -321,8 +321,8 @@ public static bool Is(this Type typeToCheck, Type baseOrInterfaceType)
                 //
                 // Try "Type.GetInterface()" first, if possible.
                 //
-                // "Type.GetInterface()" doesn't work for nested classes (detectable by the "+" in the type name).
-                if (!baseTypeFullName.Contains('+'))
+                // "Type.GetInterface()" doesn't work for nested interfaces.
+                if (!baseOrInterfaceType.IsNested)
                 {
                     try
                     {