diff --git a/src/utilities/__tests__/buildASTSchema-test.js b/src/utilities/__tests__/buildASTSchema-test.js
index 25a353a8691..666ff7b9522 100644
--- a/src/utilities/__tests__/buildASTSchema-test.js
+++ b/src/utilities/__tests__/buildASTSchema-test.js
@@ -12,7 +12,7 @@ import { parse } from '../../language/parser';
 import { print } from '../../language/printer';
 
 import { validateSchema } from '../../type/validate';
-import { __Schema } from '../../type/introspection';
+import { __Schema, __EnumValue } from '../../type/introspection';
 import {
   assertDirective,
   GraphQLSkipDirective,
@@ -1089,6 +1089,19 @@ describe('Schema Builder', () => {
     expect(schema.getType('__Schema')).to.equal(__Schema);
   });
 
+  it('Allows to reference introspection types', () => {
+    const schema = buildSchema(`
+      type Query {
+        introspectionField: __EnumValue
+      }
+    `);
+
+    expect(
+      schema.getType('Query').getFields()['introspectionField'].type,
+    ).to.equal(__EnumValue);
+    expect(schema.getType('__EnumValue')).to.equal(__EnumValue);
+  });
+
   it('Rejects invalid SDL', () => {
     const sdl = `
       type Query {
diff --git a/src/validation/__tests__/KnownTypeNamesRule-test.js b/src/validation/__tests__/KnownTypeNamesRule-test.js
index adfe354a281..584ecab1198 100644
--- a/src/validation/__tests__/KnownTypeNamesRule-test.js
+++ b/src/validation/__tests__/KnownTypeNamesRule-test.js
@@ -35,11 +35,16 @@ function expectValidSDL(sdlStr, schema) {
 describe('Validate: Known type names', () => {
   it('known type names are valid', () => {
     expectValid(`
-      query Foo($var: String, $required: [String!]!) {
+      query Foo(
+        $var: String
+        $required: [Int!]!
+        $introspectionType: __EnumValue
+      ) {
         user(id: 4) {
           pets { ... on Pet { name }, ...PetFields, ... { name } }
         }
       }
+
       fragment PetFields on Pet {
         name
       }
@@ -97,7 +102,7 @@ describe('Validate: Known type names', () => {
   });
 
   describe('within SDL', () => {
-    it('use standard scalars', () => {
+    it('use standard types', () => {
       expectValidSDL(`
         type Query {
           string: String
@@ -105,6 +110,7 @@ describe('Validate: Known type names', () => {
           float: Float
           boolean: Boolean
           id: ID
+          introspectionType: __EnumValue
         }
       `);
     });
@@ -239,7 +245,7 @@ describe('Validate: Known type names', () => {
       ]);
     });
 
-    it('reference standard scalars inside extension document', () => {
+    it('reference standard types inside extension document', () => {
       const schema = buildSchema('type Foo');
       const sdl = `
         type SomeType {
@@ -248,6 +254,7 @@ describe('Validate: Known type names', () => {
           float: Float
           boolean: Boolean
           id: ID
+          introspectionType: __EnumValue
         }
       `;
 
diff --git a/src/validation/rules/KnownTypeNamesRule.js b/src/validation/rules/KnownTypeNamesRule.js
index 80f44c38668..357a0533d72 100644
--- a/src/validation/rules/KnownTypeNamesRule.js
+++ b/src/validation/rules/KnownTypeNamesRule.js
@@ -14,6 +14,7 @@ import {
 } from '../../language/predicates';
 
 import { specifiedScalarTypes } from '../../type/scalars';
+import { introspectionTypes } from '../../type/introspection';
 
 import {
   type ValidationContext,
@@ -49,13 +50,13 @@ export function KnownTypeNamesRule(
       if (!existingTypesMap[typeName] && !definedTypes[typeName]) {
         const definitionNode = ancestors[2] ?? parent;
         const isSDL = definitionNode != null && isSDLNode(definitionNode);
-        if (isSDL && isSpecifiedScalarName(typeName)) {
+        if (isSDL && isStandardTypeName(typeName)) {
           return;
         }
 
         const suggestedTypes = suggestionList(
           typeName,
-          isSDL ? specifiedScalarsNames.concat(typeNames) : typeNames,
+          isSDL ? standardTypeNames.concat(typeNames) : typeNames,
         );
         context.reportError(
           new GraphQLError(
@@ -68,9 +69,12 @@ export function KnownTypeNamesRule(
   };
 }
 
-const specifiedScalarsNames = specifiedScalarTypes.map((type) => type.name);
-function isSpecifiedScalarName(typeName) {
-  return specifiedScalarsNames.indexOf(typeName) !== -1;
+const standardTypeNames = [...specifiedScalarTypes, ...introspectionTypes].map(
+  (type) => type.name,
+);
+
+function isStandardTypeName(typeName) {
+  return standardTypeNames.indexOf(typeName) !== -1;
 }
 
 function isSDLNode(value: ASTNode | $ReadOnlyArray<ASTNode>): boolean {