diff --git a/src/Language/AST/DefinitionNode.php b/src/Language/AST/DefinitionNode.php
index f5a6c28..4c099cc 100644
--- a/src/Language/AST/DefinitionNode.php
+++ b/src/Language/AST/DefinitionNode.php
@@ -4,8 +4,8 @@ namespace GraphQL\Language\AST;
 interface DefinitionNode
 {
 /**
- * export type DefinitionNode = OperationDefinitionNode
- *                        | FragmentDefinitionNode
- *                        | TypeSystemDefinitionNode // experimental non-spec addition.
+ * export type DefinitionNode =
+ *   | ExecutableDefinitionNode
+ *   | TypeSystemDefinitionNode; // experimental non-spec addition.
  */
 }
diff --git a/src/Language/AST/ExecutableDefinitionNode.php b/src/Language/AST/ExecutableDefinitionNode.php
new file mode 100644
index 0000000..6b3b572
--- /dev/null
+++ b/src/Language/AST/ExecutableDefinitionNode.php
@@ -0,0 +1,11 @@
+<?php
+namespace GraphQL\Language\AST;
+
+interface ExecutableDefinitionNode extends DefinitionNode
+{
+/**
+ * export type ExecutableDefinitionNode =
+ *   | OperationDefinitionNode
+ *   | FragmentDefinitionNode;
+ */
+}
diff --git a/src/Language/AST/FragmentDefinitionNode.php b/src/Language/AST/FragmentDefinitionNode.php
index 306cac6..04193b1 100644
--- a/src/Language/AST/FragmentDefinitionNode.php
+++ b/src/Language/AST/FragmentDefinitionNode.php
@@ -1,7 +1,7 @@
 <?php
 namespace GraphQL\Language\AST;
 
-class FragmentDefinitionNode extends Node implements DefinitionNode, HasSelectionSet
+class FragmentDefinitionNode extends Node implements ExecutableDefinitionNode, HasSelectionSet
 {
     public $kind = NodeKind::FRAGMENT_DEFINITION;
 
diff --git a/src/Language/AST/OperationDefinitionNode.php b/src/Language/AST/OperationDefinitionNode.php
index 0fb6e7b..13b7100 100644
--- a/src/Language/AST/OperationDefinitionNode.php
+++ b/src/Language/AST/OperationDefinitionNode.php
@@ -1,7 +1,7 @@
 <?php
 namespace GraphQL\Language\AST;
 
-class OperationDefinitionNode extends Node implements DefinitionNode, HasSelectionSet
+class OperationDefinitionNode extends Node implements ExecutableDefinitionNode, HasSelectionSet
 {
     /**
      * @var string
diff --git a/src/Language/Parser.php b/src/Language/Parser.php
index b843f3d..3cdc211 100644
--- a/src/Language/Parser.php
+++ b/src/Language/Parser.php
@@ -6,6 +6,7 @@ use GraphQL\Language\AST\DirectiveDefinitionNode;
 use GraphQL\Language\AST\EnumTypeDefinitionNode;
 use GraphQL\Language\AST\EnumTypeExtensionNode;
 use GraphQL\Language\AST\EnumValueDefinitionNode;
+use GraphQL\Language\AST\ExecutableDefinitionNode;
 use GraphQL\Language\AST\FieldDefinitionNode;
 use GraphQL\Language\AST\InputObjectTypeDefinitionNode;
 use GraphQL\Language\AST\InputObjectTypeExtensionNode;
@@ -328,24 +329,18 @@ class Parser
     }
 
     /**
-     * @return OperationDefinitionNode|FragmentDefinitionNode|TypeSystemDefinitionNode
+     * @return ExecutableDefinitionNode|TypeSystemDefinitionNode
      * @throws SyntaxError
      */
     function parseDefinition()
     {
-        if ($this->peek(Token::BRACE_L)) {
-            return $this->parseOperationDefinition();
-        }
-
         if ($this->peek(Token::NAME)) {
             switch ($this->lexer->token->value) {
                 case 'query':
                 case 'mutation':
                 case 'subscription':
-                    return $this->parseOperationDefinition();
-
                 case 'fragment':
-                    return $this->parseFragmentDefinition();
+                    return $this->parseExecutableDefinition();
 
                 // Note: The schema definition language is an experimental addition.
                 case 'schema':
@@ -357,13 +352,37 @@ class Parser
                 case 'input':
                 case 'extend':
                 case 'directive':
+                    // Note: The schema definition language is an experimental addition.
                     return $this->parseTypeSystemDefinition();
             }
+        } else if ($this->peek(Token::BRACE_L)) {
+            return $this->parseExecutableDefinition();
+        } else if ($this->peekDescription()) {
+            // Note: The schema definition language is an experimental addition.
+            return $this->parseTypeSystemDefinition();
         }
 
-        // Note: The schema definition language is an experimental addition.
-        if ($this->peekDescription()) {
-            return $this->parseTypeSystemDefinition();
+        throw $this->unexpected();
+    }
+
+    /**
+     * @return ExecutableDefinitionNode
+     * @throws SyntaxError
+     */
+    function parseExecutableDefinition()
+    {
+        if ($this->peek(Token::NAME)) {
+            switch ($this->lexer->token->value) {
+                case 'query':
+                case 'mutation':
+                case 'subscription':
+                    return $this->parseOperationDefinition();
+
+                case 'fragment':
+                    return $this->parseFragmentDefinition();
+            }
+        } else if ($this->peek(Token::BRACE_L)) {
+            return $this->parseOperationDefinition();
         }
 
         throw $this->unexpected();