diff --git a/packages/core/schematics/test/undecorated_classes_with_decorated_fields_migration_spec.ts b/packages/core/schematics/test/undecorated_classes_with_decorated_fields_migration_spec.ts
index 27c7ac65f2..e82adc2462 100644
--- a/packages/core/schematics/test/undecorated_classes_with_decorated_fields_migration_spec.ts
+++ b/packages/core/schematics/test/undecorated_classes_with_decorated_fields_migration_spec.ts
@@ -42,7 +42,7 @@ describe('Undecorated classes with decorated fields migration', () => {
     shx.rm('-r', tmpDirPath);
   });
 
-  it(`should add an import for Directive if there isn't one already`, async() => {
+  it(`should add an import for Directive if there isn't one already`, async () => {
     writeFile('/index.ts', `
       import { Input } from '@angular/core';
 
@@ -56,7 +56,7 @@ describe('Undecorated classes with decorated fields migration', () => {
         .toContain(`import { Input, Directive } from '@angular/core';`);
   });
 
-  it('should not change the imports if there is an import for Directive already', async() => {
+  it('should not change the imports if there is an import for Directive already', async () => {
     writeFile('/index.ts', `
       import { Directive, Input } from '@angular/core';
 
@@ -74,8 +74,9 @@ describe('Undecorated classes with decorated fields migration', () => {
         .toContain(`import { Directive, Input } from '@angular/core';`);
   });
 
-  it('should not generate conflicting imports there is a different `Directive` symbol', async() => {
-    writeFile('/index.ts', `
+  it('should not generate conflicting imports there is a different `Directive` symbol',
+     async () => {
+       writeFile('/index.ts', `
       import { HostBinding } from '@angular/core';
       
       export class Directive {
@@ -88,14 +89,14 @@ describe('Undecorated classes with decorated fields migration', () => {
       }
     `);
 
-    await runMigration();
-    const fileContent = tree.readContent('/index.ts');
-    expect(fileContent)
-        .toContain(`import { HostBinding, Directive as Directive_1 } from '@angular/core';`);
-    expect(fileContent).toMatch(/@Directive_1\(\)\s+export class MyLibrarySharedBaseClass/);
-  });
+       await runMigration();
+       const fileContent = tree.readContent('/index.ts');
+       expect(fileContent)
+           .toContain(`import { HostBinding, Directive as Directive_1 } from '@angular/core';`);
+       expect(fileContent).toMatch(/@Directive_1\(\)\s+export class MyLibrarySharedBaseClass/);
+     });
 
-  it('should add @Directive to undecorated classes that have @Input', async() => {
+  it('should add @Directive to undecorated classes that have @Input', async () => {
     writeFile('/index.ts', `
       import { Input } from '@angular/core';
 
@@ -108,7 +109,7 @@ describe('Undecorated classes with decorated fields migration', () => {
     expect(tree.readContent('/index.ts')).toContain(`@Directive()\nexport class Base {`);
   });
 
-  it('should not change decorated classes', async() => {
+  it('should not change decorated classes', async () => {
     writeFile('/index.ts', `
       import { Input, Component, Output, EventEmitter } from '@angular/core';
 
@@ -130,7 +131,7 @@ describe('Undecorated classes with decorated fields migration', () => {
     expect(content).toContain(`@Directive()\nexport class Child extends Base {`);
   });
 
-  it('should add @Directive to undecorated classes that have @Output', async() => {
+  it('should add @Directive to undecorated classes that have @Output', async () => {
     writeFile('/index.ts', `
       import { Output, EventEmitter } from '@angular/core';
 
@@ -143,7 +144,7 @@ describe('Undecorated classes with decorated fields migration', () => {
     expect(tree.readContent('/index.ts')).toContain(`@Directive()\nexport class Base {`);
   });
 
-  it('should add @Directive to undecorated classes that have a host binding', async() => {
+  it('should add @Directive to undecorated classes that have a host binding', async () => {
     writeFile('/index.ts', `
       import { HostBinding } from '@angular/core';
 
@@ -159,7 +160,7 @@ describe('Undecorated classes with decorated fields migration', () => {
     expect(tree.readContent('/index.ts')).toContain(`@Directive()\nexport class Base {`);
   });
 
-  it('should add @Directive to undecorated classes that have a host listener', async() => {
+  it('should add @Directive to undecorated classes that have a host listener', async () => {
     writeFile('/index.ts', `
       import { HostListener } from '@angular/core';
 
@@ -175,7 +176,7 @@ describe('Undecorated classes with decorated fields migration', () => {
     expect(tree.readContent('/index.ts')).toContain(`@Directive()\nexport class Base {`);
   });
 
-  it('should add @Directive to undecorated classes that have a ViewChild query', async() => {
+  it('should add @Directive to undecorated classes that have a ViewChild query', async () => {
     writeFile('/index.ts', `
       import { ViewChild, ElementRef } from '@angular/core';
 
@@ -188,7 +189,7 @@ describe('Undecorated classes with decorated fields migration', () => {
     expect(tree.readContent('/index.ts')).toContain(`@Directive()\nexport class Base {`);
   });
 
-  it('should add @Directive to undecorated classes that have a ViewChildren query', async() => {
+  it('should add @Directive to undecorated classes that have a ViewChildren query', async () => {
     writeFile('/index.ts', `
       import { ViewChildren, ElementRef } from '@angular/core';
 
@@ -201,7 +202,7 @@ describe('Undecorated classes with decorated fields migration', () => {
     expect(tree.readContent('/index.ts')).toContain(`@Directive()\nexport class Base {`);
   });
 
-  it('should add @Directive to undecorated classes that have a ContentChild query', async() => {
+  it('should add @Directive to undecorated classes that have a ContentChild query', async () => {
     writeFile('/index.ts', `
       import { ContentChild, ElementRef } from '@angular/core';
 
@@ -214,7 +215,7 @@ describe('Undecorated classes with decorated fields migration', () => {
     expect(tree.readContent('/index.ts')).toContain(`@Directive()\nexport class Base {`);
   });
 
-  it('should add @Directive to undecorated classes that have a ContentChildren query', async() => {
+  it('should add @Directive to undecorated classes that have a ContentChildren query', async () => {
     writeFile('/index.ts', `
       import { ContentChildren, ElementRef } from '@angular/core';
 
@@ -227,7 +228,7 @@ describe('Undecorated classes with decorated fields migration', () => {
     expect(tree.readContent('/index.ts')).toContain(`@Directive()\nexport class Base {`);
   });
 
-  it('should add @Directive to undecorated derived classes of a migrated class', async() => {
+  it('should add @Directive to undecorated derived classes of a migrated class', async () => {
     writeFile('/index.ts', `
       import { Input, Directive, NgModule } from '@angular/core';
 
@@ -259,7 +260,7 @@ describe('Undecorated classes with decorated fields migration', () => {
     expect(fileContent).toMatch(/}\s+export class MyCompWrapped/);
   });
 
-  it('should add @Directive to derived undecorated classes of abstract directives', async() => {
+  it('should add @Directive to derived undecorated classes of abstract directives', async () => {
     writeFile('/index.ts', `
       import { Input, Directive, NgModule } from '@angular/core';
 
@@ -292,6 +293,27 @@ describe('Undecorated classes with decorated fields migration', () => {
     expect(fileContent).toMatch(/}\s+export class MyCompWrapped/);
   });
 
+  it('should not throw if undecorated class extends from unresolved declaration', async () => {
+    writeFile('/lib.d.ts', `
+      // Fakes the ES5 error default lib types. Since we are in a virtual tree,
+      // the default lib types from TypeScript are not available.
+      interface ErrorConstructor {}
+      declare var Error: ErrorConstructor;
+    `);
+    writeFile('/index.ts', `
+      export class MyCustomErrorClass extends Error {}
+    `);
+
+    let error: any = null;
+    try {
+      await runMigration();
+    } catch (e) {
+      error = e;
+    }
+
+    expect(error).toBe(null);
+  });
+
   function writeFile(filePath: string, contents: string) {
     host.sync.write(normalize(filePath), virtualFs.stringToFileBuffer(contents));
   }
diff --git a/packages/core/schematics/utils/typescript/find_base_classes.ts b/packages/core/schematics/utils/typescript/find_base_classes.ts
index ae075bce15..f6a16c120a 100644
--- a/packages/core/schematics/utils/typescript/find_base_classes.ts
+++ b/packages/core/schematics/utils/typescript/find_base_classes.ts
@@ -20,7 +20,9 @@ export function findBaseClassDeclarations(node: ts.ClassDeclaration, typeChecker
       break;
     }
     const symbol = typeChecker.getTypeAtLocation(baseTypes[0]).getSymbol();
-    if (!symbol || !ts.isClassDeclaration(symbol.valueDeclaration)) {
+    // Note: `ts.Symbol#valueDeclaration` can be undefined. TypeScript has an incorrect type
+    // for this: https://github.com/microsoft/TypeScript/issues/24706.
+    if (!symbol || !symbol.valueDeclaration || !ts.isClassDeclaration(symbol.valueDeclaration)) {
       break;
     }
     result.push({identifier: baseTypes[0], node: symbol.valueDeclaration});