diff --git a/src/execution/__tests__/resolve.js b/src/execution/__tests__/resolve.js
new file mode 100644
index 0000000000..896b0b8919
--- /dev/null
+++ b/src/execution/__tests__/resolve.js
@@ -0,0 +1,114 @@
+/**
+ *  Copyright (c) 2015, Facebook, Inc.
+ *  All rights reserved.
+ *
+ *  This source code is licensed under the BSD-style license found in the
+ *  LICENSE file in the root directory of this source tree. An additional grant
+ *  of patent rights can be found in the PATENTS file in the same directory.
+ */
+
+import { expect } from 'chai';
+import { describe, it } from 'mocha';
+
+import {
+  graphql,
+  GraphQLSchema,
+  GraphQLObjectType,
+  GraphQLString,
+  GraphQLInt,
+} from '../../';
+
+describe('Execute: resolve function', () => {
+
+  function testSchema(testField) {
+    return new GraphQLSchema({
+      query: new GraphQLObjectType({
+        name: 'Query',
+        fields: {
+          test: testField
+        }
+      })
+    });
+  }
+
+  it('default function accesses properties', async () => {
+    const schema = testSchema({ type: GraphQLString });
+
+    const source = {
+      test: 'testValue'
+    };
+
+    expect(
+      await graphql(schema, '{ test }', source)
+    ).to.deep.equal({
+      data: {
+        test: 'testValue'
+      }
+    });
+  });
+
+  it('default function calls methods', async () => {
+    const schema = testSchema({ type: GraphQLString });
+
+    const source = {
+      _secret: 'secretValue',
+      test() {
+        return this._secret;
+      }
+    };
+
+    expect(
+      await graphql(schema, '{ test }', source)
+    ).to.deep.equal({
+      data: {
+        test: 'secretValue'
+      }
+    });
+  });
+
+  it('uses provided resolve function', async () => {
+    const schema = testSchema({
+      type: GraphQLString,
+      args: {
+        aStr: { type: GraphQLString },
+        aInt: { type: GraphQLInt },
+      },
+      resolve(source, args) {
+        return JSON.stringify([ source, args ]);
+      }
+    });
+
+    expect(
+      await graphql(schema, '{ test }')
+    ).to.deep.equal({
+      data: {
+        test: '[null,{}]'
+      }
+    });
+
+    expect(
+      await graphql(schema, '{ test }', 'Source!')
+    ).to.deep.equal({
+      data: {
+        test: '["Source!",{}]'
+      }
+    });
+
+    expect(
+      await graphql(schema, '{ test(aStr: "String!") }', 'Source!')
+    ).to.deep.equal({
+      data: {
+        test: '["Source!",{"aStr":"String!"}]'
+      }
+    });
+
+    expect(
+      await graphql(schema, '{ test(aInt: -123, aStr: "String!") }', 'Source!')
+    ).to.deep.equal({
+      data: {
+        test: '["Source!",{"aStr":"String!","aInt":-123}]'
+      }
+    });
+  });
+
+});
diff --git a/src/execution/execute.js b/src/execution/execute.js
index f419ebc156..53b9f4155c 100644
--- a/src/execution/execute.js
+++ b/src/execution/execute.js
@@ -865,11 +865,11 @@ function completeObjectValue(
  * and returns it as the result, or if it's a function, returns the result
  * of calling that function.
  */
-function defaultResolveFn(source, args, { fieldName }) {
+function defaultResolveFn(source: any, args, { fieldName }) {
   // ensure source is a value for which property access is acceptable.
-  if (typeof source !== 'number' && typeof source !== 'string' && source) {
-    const property = (source: any)[fieldName];
-    return typeof property === 'function' ? property.call(source) : property;
+  if (typeof source === 'object' || typeof source === 'function') {
+    const property = source[fieldName];
+    return typeof property === 'function' ? source[fieldName]() : property;
   }
 }