diff --git a/packages/language-service/src/typescript_host.ts b/packages/language-service/src/typescript_host.ts
index 79b06efa31..8a076f6f69 100644
--- a/packages/language-service/src/typescript_host.ts
+++ b/packages/language-service/src/typescript_host.ts
@@ -140,7 +140,7 @@ export class TypeScriptServiceHost implements LanguageServiceHost {
   }
 
   getAnalyzedModules(): NgAnalyzedModules {
-    this.validate();
+    this.updateAnalyzedModules();
     return this.ensureAnalyzedModules();
   }
 
@@ -240,7 +240,7 @@ export class TypeScriptServiceHost implements LanguageServiceHost {
 
   private validate() {
     const program = this.program;
-    if (this._staticSymbolResolver && this.lastProgram != program) {
+    if (this.lastProgram !== program) {
       // Invalidate file that have changed in the static symbol resolver
       const invalidateFile = (fileName: string) =>
           this._staticSymbolResolver.invalidateFile(fileName);
@@ -253,14 +253,18 @@ export class TypeScriptServiceHost implements LanguageServiceHost {
         const lastVersion = this.fileVersions.get(fileName);
         if (version != lastVersion) {
           this.fileVersions.set(fileName, version);
-          invalidateFile(fileName);
+          if (this._staticSymbolResolver) {
+            invalidateFile(fileName);
+          }
         }
       }
 
       // Remove file versions that are no longer in the file and invalidate them.
       const missing = Array.from(this.fileVersions.keys()).filter(f => !seen.has(f));
       missing.forEach(f => this.fileVersions.delete(f));
-      missing.forEach(invalidateFile);
+      if (this._staticSymbolResolver) {
+        missing.forEach(invalidateFile);
+      }
 
       this.lastProgram = program;
     }
@@ -634,4 +638,4 @@ function convertChain(chain: FormattedMessageChain): DiagnosticMessageChain {
 
 function errorToDiagnosticWithChain(error: FormattedError, span: Span): DeclarationError {
   return {message: error.chain ? convertChain(error.chain) : error.message, span};
-}
\ No newline at end of file
+}
diff --git a/packages/language-service/test/diagnostics_spec.ts b/packages/language-service/test/diagnostics_spec.ts
index 07a77c2872..00c1dd1fa0 100644
--- a/packages/language-service/test/diagnostics_spec.ts
+++ b/packages/language-service/test/diagnostics_spec.ts
@@ -248,7 +248,7 @@ describe('diagnostics', () => {
           template: \`
             <div *ngIf="comps | async; let comps; else loading">
             </div>
-            <ng-template #loading>Loading comps...</ng-template>            
+            <ng-template #loading>Loading comps...</ng-template>
           \`
         })
         export class MyComponent {}
diff --git a/packages/language-service/test/typescript_host_spec.ts b/packages/language-service/test/typescript_host_spec.ts
index 5bea1caf50..8f492234ee 100644
--- a/packages/language-service/test/typescript_host_spec.ts
+++ b/packages/language-service/test/typescript_host_spec.ts
@@ -46,4 +46,20 @@ describe('completions', () => {
     ngHost = new TypeScriptServiceHost(host, service);
     expect(() => ngHost.getAnalyzedModules()).not.toThrow();
   });
+
+  it('should clear the caches if program changes', () => {
+    // First create a TypescriptHost with empty script names
+    host = new MockTypescriptHost([], toh);
+    service = ts.createLanguageService(host);
+    ngHost = new TypeScriptServiceHost(host, service);
+    expect(ngHost.getAnalyzedModules().ngModules).toEqual([]);
+    // Now add a script, this would change the program
+    const fileName = '/app/main.ts';
+    const content = (host as MockTypescriptHost).getFileContent(fileName) !;
+    (host as MockTypescriptHost).addScript(fileName, content);
+    // If the caches are not cleared, we would get back an empty array.
+    // But if the caches are cleared then the analyzed modules will be non-empty.
+    expect(ngHost.getAnalyzedModules().ngModules.length).not.toEqual(0);
+  });
+
 });