diff --git a/packages/compiler-cli/src/main.ts b/packages/compiler-cli/src/main.ts
index 13ca9d5c22..050d6d089e 100644
--- a/packages/compiler-cli/src/main.ts
+++ b/packages/compiler-cli/src/main.ts
@@ -26,7 +26,7 @@ export function main(
     config?: NgcParsedConfiguration, customTransformers?: api.CustomTransformers, programReuse?: {
       program: api.Program | undefined,
     },
-    modifiedResourceFiles?: Set<string>): number {
+    modifiedResourceFiles?: Set<string>| null): number {
   let {project, rootNames, options, errors: configErrors, watch, emitFlags} =
       config || readNgcCommandLineAndConfiguration(args);
   if (configErrors.length) {
diff --git a/packages/compiler-cli/src/ngtsc/incremental/src/state.ts b/packages/compiler-cli/src/ngtsc/incremental/src/state.ts
index 983dde26a5..9f5fa79791 100644
--- a/packages/compiler-cli/src/ngtsc/incremental/src/state.ts
+++ b/packages/compiler-cli/src/ngtsc/incremental/src/state.ts
@@ -112,7 +112,7 @@ export class IncrementalState implements DependencyTracker, MetadataReader, Meta
   }
 
   private hasChangedResourceDependencies(sf: ts.SourceFile): boolean {
-    if (this.modifiedResourceFiles === undefined || !this.metadata.has(sf)) {
+    if (this.modifiedResourceFiles === null || !this.metadata.has(sf)) {
       return false;
     }
     const resourceDeps = this.metadata.get(sf) !.resourcePaths;
diff --git a/packages/compiler-cli/src/perform_compile.ts b/packages/compiler-cli/src/perform_compile.ts
index 4d27b2b323..f7ea7bbb59 100644
--- a/packages/compiler-cli/src/perform_compile.ts
+++ b/packages/compiler-cli/src/perform_compile.ts
@@ -224,7 +224,7 @@ export function exitCodeFromResult(diags: Diagnostics | undefined): number {
 export function performCompilation(
     {rootNames, options, host, oldProgram, emitCallback, mergeEmitResultsCallback,
      gatherDiagnostics = defaultGatherDiagnostics, customTransformers,
-     emitFlags = api.EmitFlags.Default, modifiedResourceFiles}: {
+     emitFlags = api.EmitFlags.Default, modifiedResourceFiles = null}: {
       rootNames: string[],
       options: api.CompilerOptions,
       host?: api.CompilerHost,
@@ -234,7 +234,7 @@ export function performCompilation(
       gatherDiagnostics?: (program: api.Program) => Diagnostics,
       customTransformers?: api.CustomTransformers,
       emitFlags?: api.EmitFlags,
-      modifiedResourceFiles?: Set<string>,
+      modifiedResourceFiles?: Set<string>| null,
     }): PerformCompilationResult {
   let program: api.Program|undefined;
   let emitResult: ts.EmitResult|undefined;
diff --git a/packages/compiler-cli/test/ngtsc/env.ts b/packages/compiler-cli/test/ngtsc/env.ts
index efb1fe6793..1f1639688d 100644
--- a/packages/compiler-cli/test/ngtsc/env.ts
+++ b/packages/compiler-cli/test/ngtsc/env.ts
@@ -26,7 +26,7 @@ import {setWrapHostForTest} from '../../src/transformers/compiler_host';
 export class NgtscTestEnvironment {
   private multiCompileHostExt: MultiCompileHostExt|null = null;
   private oldProgram: Program|null = null;
-  private changedResources: Set<string>|undefined = undefined;
+  private changedResources: Set<string>|null = null;
 
   private constructor(
       private fs: FileSystem, readonly outDir: AbsoluteFsPath, readonly basePath: AbsoluteFsPath) {}
@@ -107,6 +107,12 @@ export class NgtscTestEnvironment {
     this.multiCompileHostExt.flushWrittenFileTracking();
   }
 
+  /**
+   * Older versions of the CLI do not provide the `CompilerHost.getModifiedResourceFiles()` method.
+   * This results in the `changedResources` set being `null`.
+   */
+  simulateLegacyCLICompilerHost() { this.changedResources = null; }
+
   getFilesWrittenSinceLastFlush(): Set<string> {
     if (this.multiCompileHostExt === null) {
       throw new Error(`Not tracking written files - call enableMultipleCompilations()`);
diff --git a/packages/compiler-cli/test/ngtsc/incremental_spec.ts b/packages/compiler-cli/test/ngtsc/incremental_spec.ts
index ee288769d3..0ed8697d94 100644
--- a/packages/compiler-cli/test/ngtsc/incremental_spec.ts
+++ b/packages/compiler-cli/test/ngtsc/incremental_spec.ts
@@ -23,6 +23,23 @@ runInEachFileSystem(() => {
       env.tsconfig();
     });
 
+    it('should not crash if CLI does not provide getModifiedResourceFiles()', () => {
+      env.write('component1.ts', `
+      import {Component} from '@angular/core';
+
+      @Component({selector: 'cmp', templateUrl: './component1.template.html'})
+      export class Cmp1 {}
+    `);
+      env.write('component1.template.html', 'cmp1');
+      env.driveMain();
+
+      // Simulate a change to `component1.html`
+      env.flushWrittenFileTracking();
+      env.invalidateCachedFile('component1.html');
+      env.simulateLegacyCLICompilerHost();
+      env.driveMain();
+    });
+
     it('should skip unchanged services', () => {
       env.write('service.ts', `
       import {Injectable} from '@angular/core';