Index: src/ironruby/Compiler/Generation/RubyTypeBuilder.cs
===================================================================
--- src/ironruby/Compiler/Generation/RubyTypeBuilder.cs	(revision 42)
+++ src/ironruby/Compiler/Generation/RubyTypeBuilder.cs	(working copy)
@@ -57,7 +57,7 @@
 
             Type clrType = typeGen.FinishType();
 
-            RubyClass cls = new RubyClass(executionContext, name, clrType, null, superClass, false, false);
+            RubyClass cls = new RubyClass(executionContext, name, clrType, null, superClass, false, superClass.ShowUnderlyingTypeMembers);
 
             // set the static type field
             FieldInfo rubyClassField = clrType.GetField(".RubyClass");
Index: src/ironruby/Runtime/RubyExecutionContext.cs
===================================================================
--- src/ironruby/Runtime/RubyExecutionContext.cs	(revision 42)
+++ src/ironruby/Runtime/RubyExecutionContext.cs	(working copy)
@@ -25,6 +25,7 @@
 using Ruby.Compiler;
 using Ruby.Compiler.Generation;
 using Ruby.Hosting;
+using Microsoft.Scripting.Actions;
 
 namespace Ruby.Runtime {
 
@@ -257,6 +258,12 @@
                 return GetOrCreateClass(type);
             }
 
+            // TODO: remove when we have automatic TypeTracker => RubyClass conversions
+            TypeTracker tracker = obj as TypeTracker;
+            if (tracker != null) {
+                return GetOrCreateClass(tracker.Type);
+            }
+
             return null;
         }
 
Index: tests/ironruby/Interop/test_basic.rb
===================================================================
--- tests/ironruby/Interop/test_basic.rb	(revision 42)
+++ tests/ironruby/Interop/test_basic.rb	(working copy)
@@ -67,8 +67,25 @@
     assert_equal(Dict.new.to_string, 'System.Collections.Generic.Dictionary`2[System.String,System.String]'.to_clr_string)
 end
 
+def test_inherit
+  # TODO: more interesting tests when more features of .NET interop are working
+  class Bob < System::Collections::ArrayList
+    def foo
+      count
+    end
+  end
+
+  a = Bob.new
+  a.add 1
+  a.Add 2
+  a.add 3
+  assert_equal(a.foo, 3)
+  assert_equal(a.Count, 3)
+end
+
 test_event
 #test_field
 test_string
 test_stringbuilder
 test_generictypes
+test_inherit