diff --git a/gql_build/CHANGELOG.md b/gql_build/CHANGELOG.md
index bdb73dad4..cda168364 100644
--- a/gql_build/CHANGELOG.md
+++ b/gql_build/CHANGELOG.md
@@ -1,3 +1,7 @@
+## 0.0.9
+
+- add `__typename` field to interface and object types
+
 ## 0.0.8
 
 - escape reserved and private names
diff --git a/gql_build/lib/src/data_builder.dart b/gql_build/lib/src/data_builder.dart
index 5cd67769f..834680cd8 100644
--- a/gql_build/lib/src/data_builder.dart
+++ b/gql_build/lib/src/data_builder.dart
@@ -1,8 +1,8 @@
 import "dart:async";
 
 import "package:build/build.dart";
-
 import "package:gql_build/src/config.dart";
+import "package:gql_build/src/utils/add_introspection.dart";
 import "package:gql_build/src/utils/reader.dart";
 import "package:gql_build/src/utils/writer.dart";
 import "package:gql_code_builder/data.dart";
@@ -26,7 +26,7 @@ class DataBuilder implements Builder {
 
     final library = buildDataLibrary(
       doc,
-      schema,
+      addTypenames(schema),
     );
 
     return writeDocument(
diff --git a/gql_build/lib/src/utils/add_introspection.dart b/gql_build/lib/src/utils/add_introspection.dart
new file mode 100644
index 000000000..c8e9993a1
--- /dev/null
+++ b/gql_build/lib/src/utils/add_introspection.dart
@@ -0,0 +1,60 @@
+import "package:gql/ast.dart";
+import "package:gql_code_builder/source.dart";
+
+const typenameField = FieldDefinitionNode(
+  name: NameNode(
+    value: "__typename",
+  ),
+  type: NamedTypeNode(
+    name: NameNode(
+      value: "String",
+    ),
+    isNonNull: true,
+  ),
+);
+
+class AddTypenameField extends TransformingVisitor {
+  @override
+  ObjectTypeDefinitionNode visitObjectTypeDefinitionNode(
+    ObjectTypeDefinitionNode node,
+  ) =>
+      ObjectTypeDefinitionNode(
+        name: node.name,
+        description: node.description,
+        directives: node.directives,
+        fields: [
+          typenameField,
+          ...node.fields,
+        ],
+        interfaces: node.interfaces,
+        span: node.span,
+      );
+
+  @override
+  InterfaceTypeDefinitionNode visitInterfaceTypeDefinitionNode(
+    InterfaceTypeDefinitionNode node,
+  ) =>
+      InterfaceTypeDefinitionNode(
+        name: node.name,
+        fields: [
+          typenameField,
+          ...node.fields,
+        ],
+        directives: node.directives,
+        description: node.description,
+        span: node.span,
+      );
+}
+
+DocumentNode _transform(DocumentNode doc) => transform(
+      doc,
+      [
+        AddTypenameField(),
+      ],
+    );
+
+SourceNode addTypenames(SourceNode source) => SourceNode(
+      url: source.url,
+      document: _transform(source.document),
+      imports: source.imports.map(addTypenames).toSet(),
+    );
diff --git a/gql_build/lib/src/var_builder.dart b/gql_build/lib/src/var_builder.dart
index 2ccb0ea5b..487a43fc0 100644
--- a/gql_build/lib/src/var_builder.dart
+++ b/gql_build/lib/src/var_builder.dart
@@ -2,6 +2,7 @@ import "dart:async";
 
 import "package:build/build.dart";
 import "package:gql_build/src/config.dart";
+import "package:gql_build/src/utils/add_introspection.dart";
 import "package:gql_build/src/utils/reader.dart";
 import "package:gql_build/src/utils/writer.dart";
 import "package:gql_code_builder/var.dart";
@@ -25,7 +26,7 @@ class VarBuilder implements Builder {
 
     final library = buildVarLibrary(
       doc,
-      schema,
+      addTypenames(schema),
     );
 
     return writeDocument(
diff --git a/gql_build/pubspec.yaml b/gql_build/pubspec.yaml
index b8abd7c6e..7ee3958c9 100644
--- a/gql_build/pubspec.yaml
+++ b/gql_build/pubspec.yaml
@@ -1,19 +1,19 @@
 name: gql_build
 author: Klāvs Priedītis <klavs@prieditis.lv>
-version: 0.0.8
+version: 0.0.9
 homepage: https://github.com/gql-dart/gql/tree/master/gql_build
 description: Useful builders for your GraphQL SDL and documents. Based on package:gql_code_builder and package:build
-environment: 
-  sdk: '>=2.2.2 <3.0.0'
-dependencies: 
+environment:
+  sdk: ">=2.2.2 <3.0.0"
+dependencies:
   gql: ^0.12.1
   path: ^1.6.4
   glob: ^1.2.0
   build: ^1.0.0
-  gql_code_builder: ^0.0.8
+  gql_code_builder: ^0.0.9
   code_builder: ^3.2.0
   dart_style: ^1.2.9
-dev_dependencies: 
+dev_dependencies:
   test: ^1.0.0
   build_test: ^0.10.7
   gql_pedantic: ^1.0.1
diff --git a/gql_code_builder/CHANGELOG.md b/gql_code_builder/CHANGELOG.md
index 3de1e90f4..227690389 100644
--- a/gql_code_builder/CHANGELOG.md
+++ b/gql_code_builder/CHANGELOG.md
@@ -1,3 +1,7 @@
+## 0.0.9
+
+- remove duplicate ast imports
+
 ## 0.0.8
 
 - escape reserved and private names
diff --git a/gql_code_builder/lib/source.dart b/gql_code_builder/lib/source.dart
index 1ea19dc29..3f6f68d03 100644
--- a/gql_code_builder/lib/source.dart
+++ b/gql_code_builder/lib/source.dart
@@ -24,7 +24,7 @@ class SourceNode {
         ],
       );
 
-  List<Reference> getRefs() => [
+  Set<Reference> getRefs() => {
         ...document.definitions.map(
           (definition) => Reference(
             _getName(definition),
@@ -34,7 +34,7 @@ class SourceNode {
         ...imports.expand(
           (import) => import.getRefs(),
         ),
-      ];
+      };
 }
 
 String _getName(DefinitionNode def) {
diff --git a/gql_code_builder/pubspec.yaml b/gql_code_builder/pubspec.yaml
index ea0b5a10b..152cc43a0 100644
--- a/gql_code_builder/pubspec.yaml
+++ b/gql_code_builder/pubspec.yaml
@@ -1,14 +1,14 @@
 name: gql_code_builder
 author: Klāvs Priedītis <klavs@prieditis.lv>
-version: 0.0.8
+version: 0.0.9
 homepage: https://github.com/gql-dart/gql/tree/master/gql_code_builder
 description: Dart code builders taking *.graphql documents and SDL to build useful classes.
-environment: 
-  sdk: '>=2.2.2 <3.0.0'
-dependencies: 
+environment:
+  sdk: ">=2.2.2 <3.0.0"
+dependencies:
   gql: ^0.12.1
   code_builder: ^3.2.0
   meta: ^1.1.7
   built_collection: ^4.0.0
-dev_dependencies: 
+dev_dependencies:
   gql_pedantic: ^1.0.1