diff --git a/src/Executor/Executor.php b/src/Executor/Executor.php
index 7ef5fa0..a52f239 100644
--- a/src/Executor/Executor.php
+++ b/src/Executor/Executor.php
@@ -918,7 +918,7 @@ class Executor
             }
         }
 
-        return $property instanceof \Closure ? $property($source, $args, $context) : $property;
+        return is_callable($property) ? $property($source, $args, $context) : $property;
     }
 
     /**
diff --git a/tests/Executor/ResolveTest.php b/tests/Executor/ResolveTest.php
index f3f6cf4..a459c9e 100644
--- a/tests/Executor/ResolveTest.php
+++ b/tests/Executor/ResolveTest.php
@@ -60,6 +60,30 @@ class ResolveTest extends \PHPUnit_Framework_TestCase
         );
     }
 
+    /**
+     * @it default function calls callables
+     */
+    public function testDefaultFunctionCallsCallables()
+    {
+        $schema = $this->buildSchema(['type' => Type::string()]);
+        $_secret = 'secretValue' . uniqid();
+
+        $source = [
+            'test' => new class($_secret) {
+                public function __construct($_secret) {
+                    $this->_secret = $_secret;
+                }
+                public function __invoke() {
+                    return $this->_secret;
+                }
+            }
+        ];
+        $this->assertEquals(
+            ['data' => ['test' => $_secret]],
+            GraphQL::execute($schema, '{ test }', $source)
+        );
+    }
+
     /**
      * @it default function passes args and context
      */
@@ -114,4 +138,4 @@ class ResolveTest extends \PHPUnit_Framework_TestCase
             GraphQL::execute($schema, '{ test(aInt: -123, aStr: "String!") }', 'Source!')
         );
     }
-}
\ No newline at end of file
+}