diff --git a/src/language/__tests__/schema-parser-test.js b/src/language/__tests__/schema-parser-test.js
index 1c9fe0f144c..c35e99a4f3b 100644
--- a/src/language/__tests__/schema-parser-test.js
+++ b/src/language/__tests__/schema-parser-test.js
@@ -263,6 +263,66 @@ extend type Hello {
     );
   });
 
+  it('Schema extension', () => {
+    const body = `
+      extend schema {
+        mutation: Mutation
+      }`;
+    const doc = parse(body);
+    const expected = {
+      kind: 'Document',
+      definitions: [
+        {
+          kind: 'SchemaExtension',
+          directives: [],
+          operationTypes: [
+            {
+              kind: 'OperationTypeDefinition',
+              operation: 'mutation',
+              type: typeNode('Mutation', { start: 41, end: 49 }),
+              loc: { start: 31, end: 49 },
+            },
+          ],
+          loc: { start: 7, end: 57 },
+        },
+      ],
+      loc: { start: 0, end: 57 },
+    };
+    expect(printJson(doc)).to.equal(printJson(expected));
+  });
+
+  it('Schema extension with only directives', () => {
+    const body = 'extend schema @directive';
+    const doc = parse(body);
+    const expected = {
+      kind: 'Document',
+      definitions: [
+        {
+          kind: 'SchemaExtension',
+          directives: [
+            {
+              kind: 'Directive',
+              name: nameNode('directive', { start: 15, end: 24 }),
+              arguments: [],
+              loc: { start: 14, end: 24 },
+            },
+          ],
+          operationTypes: [],
+          loc: { start: 0, end: 24 },
+        },
+      ],
+      loc: { start: 0, end: 24 },
+    };
+    expect(printJson(doc)).to.equal(printJson(expected));
+  });
+
+  it('Schema extension without anything throws', () => {
+    expectSyntaxError('extend schema', 'Unexpected <EOF>', {
+      line: 1,
+      column: 14,
+    });
+  });
+
   it('Simple non-null type', () => {
     const body = `
 type Hello {
diff --git a/src/validation/__tests__/ExecutableDefinitions-test.js b/src/validation/__tests__/ExecutableDefinitions-test.js
index 3a626a31430..922420bb32e 100644
--- a/src/validation/__tests__/ExecutableDefinitions-test.js
+++ b/src/validation/__tests__/ExecutableDefinitions-test.js
@@ -87,10 +87,13 @@ describe('Validate: Executable definitions', () => {
       type Query {
         test: String
       }
+
+      extend schema @directive
     `,
       [
         nonExecutableDefinition('schema', 2, 7),
         nonExecutableDefinition('Query', 6, 7),
+        nonExecutableDefinition('schema', 10, 7),
       ],
     );
   });
diff --git a/src/validation/__tests__/KnownDirectives-test.js b/src/validation/__tests__/KnownDirectives-test.js
index ae460296509..0e0daf5641f 100644
--- a/src/validation/__tests__/KnownDirectives-test.js
+++ b/src/validation/__tests__/KnownDirectives-test.js
@@ -178,6 +178,8 @@ describe('Validate: Known directives', () => {
         schema @onSchema {
           query: MyQuery
         }
+
+        extend schema @onSchema
       `,
       );
     });
@@ -209,6 +211,8 @@ describe('Validate: Known directives', () => {
         schema @onObject {
           query: MyQuery
         }
+
+        extend schema @onObject
       `,
         [
           misplacedDirective('onInterface', 'OBJECT', 2, 43),
@@ -249,6 +253,7 @@ describe('Validate: Known directives', () => {
             24,
           ),
           misplacedDirective('onObject', 'SCHEMA', 22, 16),
+          misplacedDirective('onObject', 'SCHEMA', 26, 23),
         ],
       );
     });