diff --git a/README.md b/README.md
index 3188a5c..c9e9729 100644
--- a/README.md
+++ b/README.md
@@ -122,7 +122,7 @@ var {nodeInterface, nodeField} = nodeDefinitions(
 var factionType = new GraphQLObjectType({
   name: 'Faction',
   fields: () => ({
-    id: globalIdField('Faction'),
+    id: globalIdField(),
   }),
   interfaces: [nodeInterface]
 });
diff --git a/src/__tests__/starWarsSchema.js b/src/__tests__/starWarsSchema.js
index c73e661..2ed87cc 100644
--- a/src/__tests__/starWarsSchema.js
+++ b/src/__tests__/starWarsSchema.js
@@ -152,7 +152,7 @@ var shipType = new GraphQLObjectType({
   name: 'Ship',
   description: 'A ship in the Star Wars saga',
   fields: () => ({
-    id: globalIdField('Ship'),
+    id: globalIdField(),
     name: {
       type: GraphQLString,
       description: 'The name of the ship.',
@@ -194,7 +194,7 @@ var factionType = new GraphQLObjectType({
   name: 'Faction',
   description: 'A faction in the Star Wars saga',
   fields: () => ({
-    id: globalIdField('Faction'),
+    id: globalIdField(),
     name: {
       type: GraphQLString,
       description: 'The name of the faction.',
diff --git a/src/node/__tests__/global.js b/src/node/__tests__/global.js
index 6a4f71d..37bbe2c 100644
--- a/src/node/__tests__/global.js
+++ b/src/node/__tests__/global.js
@@ -48,20 +48,35 @@ var photoData = {
   },
 };
 
+var postData = {
+  '1': {  // eslint-disable-line quote-props
+    id: 1,
+    text: 'lorem'
+  },
+  '2': {  // eslint-disable-line quote-props
+    id: 2,
+    text: 'ipsum'
+  },
+};
+
 var {nodeField, nodeInterface} = nodeDefinitions(
   (globalId) => {
     var {type, id} = fromGlobalId(globalId);
     if (type === 'User') {
       return userData[id];
-    } else {
+    } else if (type === 'Photo') {
       return photoData[id];
+    } else {
+      return postData[id];
     }
   },
   (obj) => {
-    if (obj.id) {
+    if (obj.name) {
       return userType;
-    } else {
+    } else if (obj.photoId) {
       return photoType;
+    } else {
+      return postType;
     }
   }
 );
@@ -88,13 +103,28 @@ var photoType = new GraphQLObjectType({
   interfaces: [nodeInterface]
 });
 
+var postType = new GraphQLObjectType({
+  name: 'Post',
+  fields: () => ({
+    id: globalIdField(),
+    text: {
+      type: GraphQLString,
+    },
+  }),
+  interfaces: [nodeInterface]
+});
+
 var queryType = new GraphQLObjectType({
   name: 'Query',
   fields: () => ({
     node: nodeField,
     allObjects: {
       type: new GraphQLList(nodeInterface),
-      resolve: () => [userData[1], userData[2], photoData[1], photoData[2]]
+      resolve: () => [
+        userData[1], userData[2],
+        photoData[1], photoData[2],
+        postData[1], postData[2],
+      ]
     }
   })
 });
@@ -124,6 +154,12 @@ describe('global ID fields', () => {
         {
           id: 'UGhvdG86Mg=='
         },
+        {
+          id: 'UG9zdDox'
+        },
+        {
+          id: 'UG9zdDoy'
+        },
       ]
     };
 
@@ -143,6 +179,12 @@ describe('global ID fields', () => {
         ... on Photo {
           width
         }
+      },
+      post: node(id: "UG9zdDox") {
+        id
+        ... on Post {
+          text
+        }
       }
     }`;
     var expected = {
@@ -153,6 +195,10 @@ describe('global ID fields', () => {
       photo: {
         id: 'UGhvdG86MQ==',
         width: 300
+      },
+      post: {
+        id: 'UG9zdDox',
+        text: 'lorem'
       }
     };
 
diff --git a/src/node/node.js b/src/node/node.js
index 96dd45c..7aeb3f7 100644
--- a/src/node/node.js
+++ b/src/node/node.js
@@ -108,13 +108,16 @@ export function fromGlobalId(globalId: string): ResolvedGlobalId {
  * property on the object.
  */
 export function globalIdField(
-  typeName: string,
+  typeName?: ?string,
   idFetcher?: (object: any) => string
 ): GraphQLFieldConfig {
   return {
     name: 'id',
     description: 'The ID of an object',
     type: new GraphQLNonNull(GraphQLID),
-    resolve: (obj) => toGlobalId(typeName, idFetcher ? idFetcher(obj) : obj.id)
+    resolve: (obj, args, {parentType}) => toGlobalId(
+      typeName != null ? typeName : parentType.name,
+      idFetcher ? idFetcher(obj) : obj.id
+    )
   };
 }