diff --git a/modules/@angular/compiler/src/aot/static_symbol.ts b/modules/@angular/compiler/src/aot/static_symbol.ts
index 66c195e53b..02f137907d 100644
--- a/modules/@angular/compiler/src/aot/static_symbol.ts
+++ b/modules/@angular/compiler/src/aot/static_symbol.ts
@@ -6,10 +6,6 @@
  * found in the LICENSE file at https://angular.io/license
  */
 
-export function isStaticSymbol(value: any): value is StaticSymbol {
-  return typeof value === 'object' && value !== null && value['name'] && value['filePath'];
-}
-
 /**
  * A token representing the a reference to a static type.
  *
diff --git a/modules/@angular/compiler/src/aot/summary_resolver.ts b/modules/@angular/compiler/src/aot/summary_resolver.ts
index 7a36549be7..7f9709bc4f 100644
--- a/modules/@angular/compiler/src/aot/summary_resolver.ts
+++ b/modules/@angular/compiler/src/aot/summary_resolver.ts
@@ -10,7 +10,7 @@ import {SummaryResolver} from '../summary_resolver';
 
 import {GeneratedFile} from './generated_file';
 import {StaticReflector} from './static_reflector';
-import {StaticSymbol, isStaticSymbol} from './static_symbol';
+import {StaticSymbol} from './static_symbol';
 import {filterFileByPatterns} from './utils';
 
 const STRIP_SRC_FILE_SUFFIXES = /(\.ts|\.d\.ts|\.js|\.jsx|\.tsx)$/;
@@ -43,7 +43,7 @@ export class AotSummaryResolver implements SummaryResolver {
 
   serializeSummaries(srcFileUrl: string, summaries: CompileTypeSummary[]): GeneratedFile {
     const jsonReplacer = (key: string, value: any) => {
-      if (key === 'reference' && isStaticSymbol(value)) {
+      if (key === 'reference' && value instanceof StaticSymbol) {
         // We convert the source filenames into output filenames,
         // as the generated summary file will be used when the current
         // compilation unit is used as a library
diff --git a/modules/@angular/compiler/src/compile_metadata.ts b/modules/@angular/compiler/src/compile_metadata.ts
index 846763cc6c..ea74092c5f 100644
--- a/modules/@angular/compiler/src/compile_metadata.ts
+++ b/modules/@angular/compiler/src/compile_metadata.ts
@@ -8,7 +8,7 @@
 
 import {ChangeDetectionStrategy, SchemaMetadata, Type, ViewEncapsulation} from '@angular/core';
 
-import {StaticSymbol, isStaticSymbol} from './aot/static_symbol';
+import {StaticSymbol} from './aot/static_symbol';
 import {ListWrapper} from './facade/collection';
 import {isPresent, stringify} from './facade/lang';
 import {LifecycleHooks, reflector} from './private_import_core';
@@ -87,7 +87,7 @@ export function identifierName(compileIdentifier: CompileIdentifierMetadata): st
     return null;
   }
   const ref = compileIdentifier.reference;
-  if (isStaticSymbol(ref)) {
+  if (ref instanceof StaticSymbol) {
     return ref.name;
   }
   if (ref['__anonymousType']) {
@@ -106,7 +106,7 @@ export function identifierName(compileIdentifier: CompileIdentifierMetadata): st
 
 export function identifierModuleUrl(compileIdentifier: CompileIdentifierMetadata): string {
   const ref = compileIdentifier.reference;
-  if (isStaticSymbol(ref)) {
+  if (ref instanceof StaticSymbol) {
     return ref.filePath;
   }
   return reflector.importUri(ref);
diff --git a/modules/@angular/compiler/src/identifiers.ts b/modules/@angular/compiler/src/identifiers.ts
index 112a82f45d..2d0d80cb5b 100644
--- a/modules/@angular/compiler/src/identifiers.ts
+++ b/modules/@angular/compiler/src/identifiers.ts
@@ -8,7 +8,7 @@
 
 import {ANALYZE_FOR_ENTRY_COMPONENTS, AnimationTransitionEvent, ChangeDetectionStrategy, ChangeDetectorRef, ComponentFactory, ComponentFactoryResolver, ComponentRef, ElementRef, Injector, LOCALE_ID, NgModuleFactory, QueryList, RenderComponentType, Renderer, SecurityContext, SimpleChange, TRANSLATIONS_FORMAT, TemplateRef, ViewContainerRef, ViewEncapsulation} from '@angular/core';
 
-import {StaticSymbol, isStaticSymbol} from './aot/static_symbol';
+import {StaticSymbol} from './aot/static_symbol';
 import {CompileIdentifierMetadata, CompileTokenMetadata, identifierModuleUrl, identifierName} from './compile_metadata';
 import {AnimationGroupPlayer, AnimationKeyframe, AnimationSequencePlayer, AnimationStyles, AnimationTransition, AppView, ChangeDetectorStatus, CodegenComponentFactoryResolver, ComponentRef_, DebugAppView, DebugContext, NgModuleInjector, NoOpAnimationPlayer, StaticNodeDebugInfo, TemplateRef_, UNINITIALIZED, ValueUnwrapper, ViewContainer, ViewType, balanceAnimationKeyframes, clearStyles, collectAndResolveStyles, devModeEqual, prepareFinalAnimationStyles, reflector, registerModuleFactory, renderStyles, view_utils} from './private_import_core';
 
diff --git a/modules/@angular/compiler/src/metadata_resolver.ts b/modules/@angular/compiler/src/metadata_resolver.ts
index ef34d727ba..28d20135fe 100644
--- a/modules/@angular/compiler/src/metadata_resolver.ts
+++ b/modules/@angular/compiler/src/metadata_resolver.ts
@@ -8,7 +8,7 @@
 
 import {AnimationAnimateMetadata, AnimationEntryMetadata, AnimationGroupMetadata, AnimationKeyframesSequenceMetadata, AnimationMetadata, AnimationStateDeclarationMetadata, AnimationStateMetadata, AnimationStateTransitionMetadata, AnimationStyleMetadata, AnimationWithStepsMetadata, Attribute, ChangeDetectionStrategy, Component, Directive, Host, Inject, Injectable, ModuleWithProviders, Optional, Provider, Query, SchemaMetadata, Self, SkipSelf, Type, resolveForwardRef} from '@angular/core';
 
-import {isStaticSymbol} from './aot/static_symbol';
+import {StaticSymbol} from './aot/static_symbol';
 import {assertArrayOfStrings, assertInterpolationSymbols} from './assertions';
 import * as cpl from './compile_metadata';
 import {DirectiveNormalizer} from './directive_normalizer';
@@ -863,12 +863,12 @@ function flattenAndDedupeArray(tree: any[]): Array<any> {
 }
 
 function isValidType(value: any): boolean {
-  return isStaticSymbol(value) || (value instanceof Type);
+  return (value instanceof StaticSymbol) || (value instanceof Type);
 }
 
 export function componentModuleUrl(
     reflector: ReflectorReader, type: Type<any>, cmpMetadata: Component): string {
-  if (isStaticSymbol(type)) {
+  if (type instanceof StaticSymbol) {
     return type.filePath;
   }