diff --git a/packages/compiler-cli/ngcc/src/dependencies/module_resolver.ts b/packages/compiler-cli/ngcc/src/dependencies/module_resolver.ts
index 1208744b98..b059452ec2 100644
--- a/packages/compiler-cli/ngcc/src/dependencies/module_resolver.ts
+++ b/packages/compiler-cli/ngcc/src/dependencies/module_resolver.ts
@@ -25,7 +25,7 @@ export class ModuleResolver {
   private pathMappings: ProcessedPathMapping[];
 
   constructor(private fs: FileSystem, pathMappings?: PathMappings, private relativeExtensions = [
-    '.js', '/index.js'
+    '', '.js', '/index.js'
   ]) {
     this.pathMappings = pathMappings ? this.processPathMappings(pathMappings) : [];
   }
diff --git a/packages/compiler-cli/ngcc/test/dependencies/module_resolver_spec.ts b/packages/compiler-cli/ngcc/test/dependencies/module_resolver_spec.ts
index c88856fa01..2ef140ca71 100644
--- a/packages/compiler-cli/ngcc/test/dependencies/module_resolver_spec.ts
+++ b/packages/compiler-cli/ngcc/test/dependencies/module_resolver_spec.ts
@@ -83,6 +83,12 @@ runInEachFileSystem(() => {
           const resolver = new ModuleResolver(getFileSystem());
           expect(resolver.resolveModuleImport('./y', _('/libs/local-package/index.js'))).toBe(null);
         });
+
+        it('should resolve modules that already include an extension', () => {
+          const resolver = new ModuleResolver(getFileSystem());
+          expect(resolver.resolveModuleImport('./x.js', _('/libs/local-package/index.js')))
+              .toEqual(new ResolvedRelativeModule(_('/libs/local-package/x.js')));
+        });
       });
 
       describe('with non-mapped external paths', () => {