diff --git a/ILSpy/TreeNodes/DerivedTypesTreeNode.cs b/ILSpy/TreeNodes/DerivedTypesTreeNode.cs
index d3fd992683..760685dc9a 100644
--- a/ILSpy/TreeNodes/DerivedTypesTreeNode.cs
+++ b/ILSpy/TreeNodes/DerivedTypesTreeNode.cs
@@ -73,7 +73,7 @@ internal static IEnumerable<DerivedTypesEntryNode> FindDerivedTypes(AssemblyList
 					continue;
 				var metadata = module.Metadata;
 				var assembly = module.GetTypeSystemOrNull()?.MainModule as MetadataModule;
-				if (assembly != null)
+				if (assembly == null)
 					continue;
 				foreach (var h in metadata.TypeDefinitions)
 				{
@@ -107,4 +107,4 @@ public override void Decompile(Language language, ITextOutput output, Decompilat
 			threading.Decompile(language, output, options, EnsureLazyChildren);
 		}
 	}
-}
\ No newline at end of file
+}