diff --git a/src/generator.ts b/src/generator.ts
index fb8d23b0..e188b30a 100644
--- a/src/generator.ts
+++ b/src/generator.ts
@@ -35,7 +35,10 @@ function declareEnums(ast: AST, options: Options, processed = new Set<AST>()): s
   }
 
   processed.add(ast)
-  let type = ''
+
+  if (ast.isExternalSchema && !options.declareExternallyReferenced) {
+    return ''
+  }
 
   switch (ast.type) {
     case 'ENUM':
@@ -46,7 +49,7 @@ function declareEnums(ast: AST, options: Options, processed = new Set<AST>()): s
     case 'INTERSECTION':
       return ast.params.reduce((prev, ast) => prev + declareEnums(ast, options, processed), '')
     case 'TUPLE':
-      type = ast.params.reduce((prev, ast) => prev + declareEnums(ast, options, processed), '')
+      let type = ast.params.reduce((prev, ast) => prev + declareEnums(ast, options, processed), '')
       if (ast.spreadParam) {
         type += declareEnums(ast.spreadParam, options, processed)
       }
@@ -66,15 +69,17 @@ function declareNamedInterfaces(ast: AST, options: Options, rootASTName: string,
   processed.add(ast)
   let type = ''
 
+  if (ast.isExternalSchema && !options.declareExternallyReferenced) {
+    return ''
+  }
+
   switch (ast.type) {
     case 'ARRAY':
       type = declareNamedInterfaces((ast as TArray).params, options, rootASTName, processed)
       break
     case 'INTERFACE':
       type = [
-        hasStandaloneName(ast) &&
-          (ast.standaloneName === rootASTName || options.declareExternallyReferenced) &&
-          generateStandaloneInterface(ast, options),
+        hasStandaloneName(ast) && generateStandaloneInterface(ast, options),
         getSuperTypesAndParams(ast)
           .map(ast => declareNamedInterfaces(ast, options, rootASTName, processed))
           .filter(Boolean)
@@ -108,6 +113,10 @@ function declareNamedTypes(ast: AST, options: Options, rootASTName: string, proc
 
   processed.add(ast)
 
+  if (ast.isExternalSchema && !options.declareExternallyReferenced) {
+    return ''
+  }
+
   switch (ast.type) {
     case 'ARRAY':
       return [
@@ -120,11 +129,7 @@ function declareNamedTypes(ast: AST, options: Options, rootASTName: string, proc
       return ''
     case 'INTERFACE':
       return getSuperTypesAndParams(ast)
-        .map(
-          ast =>
-            (ast.standaloneName === rootASTName || options.declareExternallyReferenced) &&
-            declareNamedTypes(ast, options, rootASTName, processed),
-        )
+        .map(ast => declareNamedTypes(ast, options, rootASTName, processed))
         .filter(Boolean)
         .join('\n')
     case 'INTERSECTION':
diff --git a/src/normalizer.ts b/src/normalizer.ts
index fa3ec6ba..7a50d082 100644
--- a/src/normalizer.ts
+++ b/src/normalizer.ts
@@ -1,4 +1,4 @@
-import {JSONSchemaTypeName, LinkedJSONSchema, NormalizedJSONSchema, Parent} from './types/JSONSchema'
+import {IsExternalSchema, JSONSchemaTypeName, LinkedJSONSchema, NormalizedJSONSchema, Parent} from './types/JSONSchema'
 import {appendToDescription, escapeBlockComment, isSchemaLike, justName, toSafeString, traverse} from './utils'
 import {Options} from './'
 import {DereferencedPaths} from './resolver'
@@ -73,6 +73,27 @@ rules.set('Transform id to $id', (schema, fileName) => {
   }
 })
 
+rules.set(
+  'Add an ExternalRef flag to anything that needs it',
+  (schema, _fileName, _options, _key, dereferencedPaths) => {
+    if (!isSchemaLike(schema)) {
+      return
+    }
+
+    // Top-level schema
+    if (!schema[Parent]) {
+      return
+    }
+
+    const dereferencedName = dereferencedPaths.get(schema)
+    Object.defineProperty(schema, IsExternalSchema, {
+      enumerable: false,
+      value: dereferencedName && !dereferencedName.startsWith('#'),
+      writable: false,
+    })
+  },
+)
+
 rules.set('Add an $id to anything that needs it', (schema, fileName, _options, _key, dereferencedPaths) => {
   if (!isSchemaLike(schema)) {
     return
@@ -95,10 +116,6 @@ rules.set('Add an $id to anything that needs it', (schema, fileName, _options, _
   if (!schema.$id && !schema.title && dereferencedName) {
     schema.$id = toSafeString(justName(dereferencedName))
   }
-
-  if (dereferencedName) {
-    dereferencedPaths.delete(schema)
-  }
 })
 
 rules.set('Escape closing JSDoc comment', schema => {
diff --git a/src/parser.ts b/src/parser.ts
index 7e82d7f6..b942e76d 100644
--- a/src/parser.ts
+++ b/src/parser.ts
@@ -23,6 +23,9 @@ import {
   JSONSchemaWithDefinitions,
   SchemaSchema,
   SchemaType,
+  IsExternalSchema,
+  NormalizedJSONSchema,
+  Parent,
 } from './types/JSONSchema'
 import {generateName, log, maybeStripDefault, maybeStripNameHints} from './utils'
 
@@ -31,7 +34,7 @@ export type Processed = Map<LinkedJSONSchema, Map<SchemaType, AST>>
 export type UsedNames = Set<string>
 
 export function parse(
-  schema: LinkedJSONSchema | JSONSchema4Type,
+  schema: NormalizedJSONSchema | JSONSchema4Type,
   options: Options,
   keyName?: string,
   processed: Processed = new Map(),
@@ -54,19 +57,17 @@ export function parse(
 
   // Be careful to first process the intersection before processing its params,
   // so that it gets first pick for standalone name.
-  const ast = parseAsTypeWithCache(
-    {
-      $id: schema.$id,
-      allOf: [],
-      description: schema.description,
-      title: schema.title,
-    },
-    'ALL_OF',
-    options,
-    keyName,
-    processed,
-    usedNames,
-  ) as TIntersection
+  const allOf: NormalizedJSONSchema = {
+    [IsExternalSchema]: schema[IsExternalSchema],
+    [Parent]: schema[Parent],
+    $id: schema.$id,
+    allOf: [],
+    description: schema.description,
+    title: schema.title,
+    additionalProperties: schema.additionalProperties,
+    required: schema.required,
+  }
+  const ast = parseAsTypeWithCache(allOf, 'ALL_OF', options, keyName, processed, usedNames) as TIntersection
 
   ast.params = types.map(type =>
     // We hoist description (for comment) and id/title (for standaloneName)
@@ -79,7 +80,7 @@ export function parse(
 }
 
 function parseAsTypeWithCache(
-  schema: LinkedJSONSchema,
+  schema: NormalizedJSONSchema,
   type: SchemaType,
   options: Options,
   keyName?: string,
@@ -111,12 +112,14 @@ function parseAsTypeWithCache(
 function parseBooleanSchema(schema: boolean, keyName: string | undefined, options: Options): AST {
   if (schema) {
     return {
+      isExternalSchema: false,
       keyName,
       type: options.unknownAny ? 'UNKNOWN' : 'ANY',
     }
   }
 
   return {
+    isExternalSchema: false,
     keyName,
     type: 'NEVER',
   }
@@ -124,6 +127,7 @@ function parseBooleanSchema(schema: boolean, keyName: string | undefined, option
 
 function parseLiteral(schema: JSONSchema4Type, keyName: string | undefined): AST {
   return {
+    isExternalSchema: false,
     keyName,
     params: schema,
     type: 'LITERAL',
@@ -131,7 +135,7 @@ function parseLiteral(schema: JSONSchema4Type, keyName: string | undefined): AST
 }
 
 function parseNonLiteral(
-  schema: LinkedJSONSchema,
+  schema: NormalizedJSONSchema,
   type: SchemaType,
   options: Options,
   keyName: string | undefined,
@@ -146,6 +150,7 @@ function parseNonLiteral(
       return {
         comment: schema.description,
         deprecated: schema.deprecated,
+        isExternalSchema: schema[IsExternalSchema],
         keyName,
         standaloneName: standaloneName(schema, keyNameFromDefinition, usedNames, options),
         params: schema.allOf!.map(_ => parse(_, options, undefined, processed, usedNames)),
@@ -156,6 +161,7 @@ function parseNonLiteral(
         ...(options.unknownAny ? T_UNKNOWN : T_ANY),
         comment: schema.description,
         deprecated: schema.deprecated,
+        isExternalSchema: schema[IsExternalSchema],
         keyName,
         standaloneName: standaloneName(schema, keyNameFromDefinition, usedNames, options),
       }
@@ -163,6 +169,7 @@ function parseNonLiteral(
       return {
         comment: schema.description,
         deprecated: schema.deprecated,
+        isExternalSchema: schema[IsExternalSchema],
         keyName,
         standaloneName: standaloneName(schema, keyNameFromDefinition, usedNames, options),
         params: schema.anyOf!.map(_ => parse(_, options, undefined, processed, usedNames)),
@@ -172,6 +179,7 @@ function parseNonLiteral(
       return {
         comment: schema.description,
         deprecated: schema.deprecated,
+        isExternalSchema: schema[IsExternalSchema],
         keyName,
         standaloneName: standaloneName(schema, keyNameFromDefinition, usedNames, options),
         type: 'BOOLEAN',
@@ -180,6 +188,7 @@ function parseNonLiteral(
       return {
         comment: schema.description,
         deprecated: schema.deprecated,
+        isExternalSchema: schema[IsExternalSchema],
         keyName,
         params: schema.tsType!,
         standaloneName: standaloneName(schema, keyNameFromDefinition, usedNames, options),
@@ -189,9 +198,10 @@ function parseNonLiteral(
       return {
         comment: schema.description,
         deprecated: schema.deprecated,
+        isExternalSchema: schema[IsExternalSchema],
         keyName,
         standaloneName: standaloneName(schema, keyNameFromDefinition ?? keyName, usedNames, options)!,
-        params: schema.enum!.map((_, n) => ({
+        params: schema.enum!.map((_: any, n: number) => ({
           ast: parseLiteral(_, undefined),
           keyName: schema.tsEnumNames![n],
         })),
@@ -203,6 +213,7 @@ function parseNonLiteral(
       return {
         comment: schema.description,
         deprecated: schema.deprecated,
+        isExternalSchema: schema[IsExternalSchema],
         keyName,
         standaloneName: standaloneName(schema, keyNameFromDefinition, usedNames, options),
         type: 'NEVER',
@@ -211,6 +222,7 @@ function parseNonLiteral(
       return {
         comment: schema.description,
         deprecated: schema.deprecated,
+        isExternalSchema: schema[IsExternalSchema],
         keyName,
         standaloneName: standaloneName(schema, keyNameFromDefinition, usedNames, options),
         type: 'NULL',
@@ -219,6 +231,7 @@ function parseNonLiteral(
       return {
         comment: schema.description,
         deprecated: schema.deprecated,
+        isExternalSchema: schema[IsExternalSchema],
         keyName,
         standaloneName: standaloneName(schema, keyNameFromDefinition, usedNames, options),
         type: 'NUMBER',
@@ -226,6 +239,7 @@ function parseNonLiteral(
     case 'OBJECT':
       return {
         comment: schema.description,
+        isExternalSchema: schema[IsExternalSchema],
         keyName,
         standaloneName: standaloneName(schema, keyNameFromDefinition, usedNames, options),
         type: 'OBJECT',
@@ -235,6 +249,7 @@ function parseNonLiteral(
       return {
         comment: schema.description,
         deprecated: schema.deprecated,
+        isExternalSchema: schema[IsExternalSchema],
         keyName,
         standaloneName: standaloneName(schema, keyNameFromDefinition, usedNames, options),
         params: schema.oneOf!.map(_ => parse(_, options, undefined, processed, usedNames)),
@@ -246,6 +261,7 @@ function parseNonLiteral(
       return {
         comment: schema.description,
         deprecated: schema.deprecated,
+        isExternalSchema: schema[IsExternalSchema],
         keyName,
         standaloneName: standaloneName(schema, keyNameFromDefinition, usedNames, options),
         type: 'STRING',
@@ -258,6 +274,7 @@ function parseNonLiteral(
         const arrayType: TTuple = {
           comment: schema.description,
           deprecated: schema.deprecated,
+          isExternalSchema: schema[IsExternalSchema],
           keyName,
           maxItems,
           minItems,
@@ -275,6 +292,7 @@ function parseNonLiteral(
         return {
           comment: schema.description,
           deprecated: schema.deprecated,
+          isExternalSchema: schema[IsExternalSchema],
           keyName,
           standaloneName: standaloneName(schema, keyNameFromDefinition, usedNames, options),
           params: parse(schema.items!, options, `{keyNameFromDefinition}Items`, processed, usedNames),
@@ -285,6 +303,7 @@ function parseNonLiteral(
       return {
         comment: schema.description,
         deprecated: schema.deprecated,
+        isExternalSchema: schema[IsExternalSchema],
         keyName,
         standaloneName: standaloneName(schema, keyNameFromDefinition, usedNames, options),
         params: (schema.type as JSONSchema4TypeName[]).map(type => {
@@ -297,9 +316,10 @@ function parseNonLiteral(
       return {
         comment: schema.description,
         deprecated: schema.deprecated,
+        isExternalSchema: schema[IsExternalSchema],
         keyName,
         standaloneName: standaloneName(schema, keyNameFromDefinition, usedNames, options),
-        params: schema.enum!.map(_ => parseLiteral(_, undefined)),
+        params: schema.enum!.map((_: any) => parseLiteral(_, undefined)),
         type: 'UNION',
       }
     case 'UNNAMED_SCHEMA':
@@ -313,6 +333,7 @@ function parseNonLiteral(
         return {
           comment: schema.description,
           deprecated: schema.deprecated,
+          isExternalSchema: schema[IsExternalSchema],
           keyName,
           maxItems: schema.maxItems,
           minItems,
@@ -328,6 +349,7 @@ function parseNonLiteral(
       return {
         comment: schema.description,
         deprecated: schema.deprecated,
+        isExternalSchema: schema[IsExternalSchema],
         keyName,
         params,
         standaloneName: standaloneName(schema, keyNameFromDefinition, usedNames, options),
@@ -364,6 +386,7 @@ function newInterface(
   return {
     comment: schema.description,
     deprecated: schema.deprecated,
+    isExternalSchema: schema[IsExternalSchema],
     keyName,
     params: parseSchema(schema, options, processed, usedNames, name),
     standaloneName: name,
diff --git a/src/types/AST.ts b/src/types/AST.ts
index 4fb05afd..a4edf1ae 100644
--- a/src/types/AST.ts
+++ b/src/types/AST.ts
@@ -24,6 +24,7 @@ export type AST =
 
 export interface AbstractAST {
   comment?: string
+  isExternalSchema: boolean
   keyName?: string
   standaloneName?: string
   type: AST_TYPE
@@ -154,18 +155,22 @@ export interface TCustomType extends AbstractAST {
 
 export const T_ANY: TAny = {
   type: 'ANY',
+  isExternalSchema: false,
 }
 
 export const T_ANY_ADDITIONAL_PROPERTIES: TAny & ASTWithName = {
   keyName: '[k: string]',
   type: 'ANY',
+  isExternalSchema: false,
 }
 
 export const T_UNKNOWN: TUnknown = {
   type: 'UNKNOWN',
+  isExternalSchema: false,
 }
 
 export const T_UNKNOWN_ADDITIONAL_PROPERTIES: TUnknown & ASTWithName = {
   keyName: '[k: string]',
   type: 'UNKNOWN',
+  isExternalSchema: false,
 }
diff --git a/src/types/JSONSchema.ts b/src/types/JSONSchema.ts
index 4c644f3f..3121027d 100644
--- a/src/types/JSONSchema.ts
+++ b/src/types/JSONSchema.ts
@@ -40,6 +40,7 @@ export interface JSONSchema extends JSONSchema4 {
   deprecated?: boolean
 }
 
+export const IsExternalSchema = Symbol('IsExternalSchema')
 export const Parent = Symbol('Parent')
 
 export interface LinkedJSONSchema extends JSONSchema {
@@ -70,7 +71,12 @@ export interface LinkedJSONSchema extends JSONSchema {
   not?: LinkedJSONSchema
 }
 
-export interface NormalizedJSONSchema extends LinkedJSONSchema {
+export type NormalizedJSONSchema = Omit<LinkedJSONSchema, 'id' | 'definitions'> & {
+  /**
+   * Indicates whether this schema was an external $ref.
+   */
+  [IsExternalSchema]: boolean
+
   additionalItems?: boolean | NormalizedJSONSchema
   additionalProperties: boolean | NormalizedJSONSchema
   extends?: string[]
@@ -92,10 +98,6 @@ export interface NormalizedJSONSchema extends LinkedJSONSchema {
   oneOf?: NormalizedJSONSchema[]
   not?: NormalizedJSONSchema
   required: string[]
-
-  // Removed by normalizer
-  definitions: never
-  id: never
 }
 
 export interface EnumJSONSchema extends NormalizedJSONSchema {
diff --git a/src/utils.ts b/src/utils.ts
index c7f1f215..2295af40 100644
--- a/src/utils.ts
+++ b/src/utils.ts
@@ -1,6 +1,6 @@
 import {deburr, isPlainObject, trim, upperFirst} from 'lodash'
 import {basename, dirname, extname, normalize, sep, posix} from 'path'
-import {JSONSchema, LinkedJSONSchema, Parent} from './types/JSONSchema'
+import {JSONSchema, LinkedJSONSchema, NormalizedJSONSchema, Parent} from './types/JSONSchema'
 import {JSONSchema4} from 'json-schema'
 import yaml from 'js-yaml'
 
@@ -338,7 +338,7 @@ export function maybeStripDefault(schema: LinkedJSONSchema): LinkedJSONSchema {
  *
  * Mutates `schema`.
  */
-export function maybeStripNameHints(schema: JSONSchema): JSONSchema {
+export function maybeStripNameHints(schema: NormalizedJSONSchema): NormalizedJSONSchema {
   if ('$id' in schema) {
     delete schema.$id
   }
diff --git a/test/__snapshots__/test/test.ts.md b/test/__snapshots__/test/test.ts.md
index e1c6e25d..4f06d5a6 100644
--- a/test/__snapshots__/test/test.ts.md
+++ b/test/__snapshots__/test/test.ts.md
@@ -1139,6 +1139,10 @@ Generated by [AVA](https://avajs.dev).
     export interface Extends extends Base1 {␊
       foo: string;␊
     }␊
+    export interface Base1 {␊
+      firstName: string;␊
+      lastName: string;␊
+    }␊
     `
 
 ## extends.2a.js
@@ -449547,26 +449551,6 @@ Generated by [AVA](https://avajs.dev).
     }␊
     `
 
-> Snapshot 5
-
-    './test/resources/MultiSchema/out/b.yaml.d.ts'
-
-> Snapshot 6
-
-    `/* eslint-disable */␊
-    /**␊
-     * This file was automatically generated by json-schema-to-typescript.␊
-     * DO NOT MODIFY IT BY HAND. Instead, modify the source JSONSchema file,␊
-     * and run json-schema-to-typescript to regenerate this file.␊
-     */␊
-    ␊
-    export interface BSchema {␊
-      x?: string;␊
-      y: number;␊
-      [k: string]: unknown;␊
-    }␊
-    `
-
 ## files in (-i), pipe out
 
 > Snapshot 1
diff --git a/test/__snapshots__/test/test.ts.snap b/test/__snapshots__/test/test.ts.snap
index 6640ff0a..f571a7e9 100644
Binary files a/test/__snapshots__/test/test.ts.snap and b/test/__snapshots__/test/test.ts.snap differ