diff --git a/lib/graphql/introspection/entry_points.rb b/lib/graphql/introspection/entry_points.rb
index 52d89eed86..82ca149001 100644
--- a/lib/graphql/introspection/entry_points.rb
+++ b/lib/graphql/introspection/entry_points.rb
@@ -15,8 +15,12 @@ def __schema
       end
 
       def __type(name:)
-        # This will probably break with non-Interpreter runtime
         type = context.warden.get_type(name)
+
+        if type && context.interpreter?
+          type = type.metadata[:type_class] || raise("Invariant: interpreter requires class-based type for #{name}")
+        end
+
         # The interpreter provides this wrapping, other execution doesnt, so support both.
         if type && !context.interpreter?
           # Apply wrapping manually since this field isn't wrapped by instrumentation
diff --git a/lib/graphql/introspection/type_type.rb b/lib/graphql/introspection/type_type.rb
index 583b87be0d..493d2b8d0c 100644
--- a/lib/graphql/introspection/type_type.rb
+++ b/lib/graphql/introspection/type_type.rb
@@ -49,7 +49,7 @@ def enum_values(include_deprecated:)
 
       def interfaces
         if @object.kind == GraphQL::TypeKinds::OBJECT
-          @context.warden.interfaces(@object)
+          @context.warden.interfaces(@object.graphql_definition)
         else
           nil
         end
@@ -57,7 +57,7 @@ def interfaces
 
       def input_fields
         if @object.kind.input_object?
-          @context.warden.arguments(@object)
+          @context.warden.arguments(@object.graphql_definition)
         else
           nil
         end
@@ -65,7 +65,7 @@ def input_fields
 
       def possible_types
         if @object.kind.abstract?
-          @context.warden.possible_types(@object)
+          @context.warden.possible_types(@object.graphql_definition)
         else
           nil
         end
@@ -75,7 +75,7 @@ def fields(include_deprecated:)
         if !@object.kind.fields?
           nil
         else
-          fields = @context.warden.fields(@object)
+          fields = @context.warden.fields(@object.graphql_definition)
           if !include_deprecated
             fields = fields.select {|f| !f.deprecation_reason }
           end
diff --git a/spec/graphql/schema/input_object_spec.rb b/spec/graphql/schema/input_object_spec.rb
index c7929ae2cc..a5aea99fbc 100644
--- a/spec/graphql/schema/input_object_spec.rb
+++ b/spec/graphql/schema/input_object_spec.rb
@@ -210,6 +210,29 @@ class TestInput2 < GraphQL::Schema::InputObject
       # assert_equal 3, input_object.dig('input_object', 'd')
       assert_equal 3, input_object.dig(:input_object, :d)
     end
+  end
 
+  describe "introspection" do
+    it "returns input fields" do
+      res = Jazz::Schema.execute('
+        {
+          __type(name: "InspectableInput") {
+            name
+            inputFields { name }
+          }
+          __schema {
+            types {
+              name
+              inputFields { name }
+            }
+          }
+        }')
+      # Test __type
+      assert_equal ["stringValue", "nestedInput", "legacyInput"], res["data"]["__type"]["inputFields"].map { |f| f["name"] }
+      # Test __schema { types }
+      # It's upcased to test custom introspection
+      input_type = res["data"]["__schema"]["types"].find { |t| t["name"] == "INSPECTABLEINPUT" }
+      assert_equal ["stringValue", "nestedInput", "legacyInput"], input_type["inputFields"].map { |f| f["name"] }
+    end
   end
 end