diff --git a/src/Type/Definition/Config.php b/src/Type/Definition/Config.php
index d5bd057..a561549 100644
--- a/src/Type/Definition/Config.php
+++ b/src/Type/Definition/Config.php
@@ -65,11 +65,30 @@ class Config
     public static function validate(array $config, array $definition)
     {
         if (self::$enableValidation) {
-            $name = isset($config['name']) ? $config['name'] : 'UnnamedType';
+            $name = isset($config['name']) ? $config['name'] : '(Unnamed Type)';
             self::validateMap($name, $config, $definition);
         }
     }
 
+    /**
+     * @param $typeName
+     * @param array $config
+     * @param array $definition
+     */
+    public static function validateField($typeName, array $config, array $definition)
+    {
+        if (self::$enableValidation) {
+            if (!isset($config['name'])) {
+                $pathStr = isset($config['type'])
+                    ? '(Unknown Field of type: ' . Utils::printSafe($config['type']) . ')'
+                    : '(Unknown Field)';
+            } else {
+                $pathStr = '';
+            }
+            self::validateMap($typeName ?: '(Unnamed Type)', $config, $definition, $pathStr);
+        }
+    }
+
     /**
      * @param $definition
      * @param int $flags
@@ -121,7 +140,10 @@ class Config
         // Make sure that all required keys are present in map
         $requiredKeys = array_filter($definitions, function($def) {return (self::getFlags($def) & self::REQUIRED) > 0;});
         $missingKeys = array_keys(array_diff_key($requiredKeys, $map));
-        Utils::invariant(empty($missingKeys), 'Error in "'.$typeName.'" type definition: Required keys missing: "%s"' . $suffix, implode(', ', $missingKeys));
+        Utils::invariant(
+            empty($missingKeys),
+            "Error in '$typeName' type definition: Required keys missing: '%s' $suffix", implode(', ', $missingKeys)
+        );
 
         // Make sure that every map value is valid given the definition
         foreach ($map as $key => $value) {
@@ -226,28 +248,28 @@ class Config
                     Utils::invariant(
                         is_callable($value) || $value instanceof InputType,
                         $err,
-                        'callable or instance of GraphQL\Type\Definition\InputType'
+                        'callable or InputType definition'
                     );
                     break;
                 case $def & self::OUTPUT_TYPE:
                     Utils::invariant(
                         is_callable($value) || $value instanceof OutputType,
                         $err,
-                        'callable or instance of GraphQL\Type\Definition\OutputType'
+                        'callable or OutputType definition'
                     );
                     break;
                 case $def & self::INTERFACE_TYPE:
                     Utils::invariant(
                         is_callable($value) || $value instanceof InterfaceType,
                         $err,
-                        'callable or instance of GraphQL\Type\Definition\InterfaceType'
+                        'callable or InterfaceType definition'
                     );
                     break;
                 case $def & self::OBJECT_TYPE:
                     Utils::invariant(
                         is_callable($value) || $value instanceof ObjectType,
                         $err,
-                        'callable or instance of GraphQL\Type\Definition\ObjectType'
+                        'callable or ObjectType definition'
                     );
                     break;
                 default:
diff --git a/src/Type/Definition/FieldDefinition.php b/src/Type/Definition/FieldDefinition.php
index 81d1c53..4d13e21 100644
--- a/src/Type/Definition/FieldDefinition.php
+++ b/src/Type/Definition/FieldDefinition.php
@@ -1,5 +1,7 @@
 <?php
 namespace GraphQL\Type\Definition;
+use GraphQL\Error\InvariantViolation;
+use GraphQL\Utils;
 
 /**
  * Class FieldDefinition
@@ -89,30 +91,39 @@ class FieldDefinition
 
     /**
      * @param array|Config $fields
+     * @param string $typeName
      * @return array
      */
-    public static function createMap(array $fields)
+    public static function createMap(array $fields, $typeName = null)
     {
         $map = [];
         foreach ($fields as $name => $field) {
             if (!is_array($field)) {
-                $field = ['type' => $field];
-            }
-            if (!isset($field['name'])) {
+                if (is_string($name)) {
+                    $field = ['name' => $name, 'type' => $field];
+                } else {
+                    throw new InvariantViolation(
+                        "Unexpected field definition for type $typeName at key $name: " . Utils::printSafe($field)
+                    );
+                }
+            } elseif (!isset($field['name']) && is_string($name)) {
                 $field['name'] = $name;
             }
-            $map[$name] = self::create($field);
+            $map[$name] = self::create($field, $typeName);
         }
         return $map;
     }
 
     /**
      * @param array|Config $field
+     * @param string $typeName
      * @return FieldDefinition
      */
-    public static function create($field)
+    public static function create($field, $typeName = null)
     {
-        Config::validate($field, self::getDefinition());
+        if ($typeName) {
+            Config::validateField($typeName, $field, self::getDefinition());
+        }
         return new self($field);
     }
 
diff --git a/src/Type/Definition/InterfaceType.php b/src/Type/Definition/InterfaceType.php
index 2d077bd..a34da04 100644
--- a/src/Type/Definition/InterfaceType.php
+++ b/src/Type/Definition/InterfaceType.php
@@ -60,7 +60,7 @@ class InterfaceType extends Type implements AbstractType, OutputType, CompositeT
             $this->fields = [];
             $fields = isset($this->config['fields']) ? $this->config['fields'] : [];
             $fields = is_callable($fields) ? call_user_func($fields) : $fields;
-            $this->fields = FieldDefinition::createMap($fields);
+            $this->fields = FieldDefinition::createMap($fields, $this->name);
         }
         return $this->fields;
     }
diff --git a/src/Type/Definition/ObjectType.php b/src/Type/Definition/ObjectType.php
index 6836e89..e094a38 100644
--- a/src/Type/Definition/ObjectType.php
+++ b/src/Type/Definition/ObjectType.php
@@ -112,7 +112,7 @@ class ObjectType extends Type implements OutputType, CompositeType
         if (null === $this->fields) {
             $fields = isset($this->config['fields']) ? $this->config['fields'] : [];
             $fields = is_callable($fields) ? call_user_func($fields) : $fields;
-            $this->fields = FieldDefinition::createMap($fields);
+            $this->fields = FieldDefinition::createMap($fields, $this->name);
         }
         return $this->fields;
     }