diff --git a/typescript/src/schema/api.ts b/typescript/src/schema/api.ts
index de917753b..5d6b5f4be 100644
--- a/typescript/src/schema/api.ts
+++ b/typescript/src/schema/api.ts
@@ -1,8 +1,12 @@
 import * as plugin from '../../../pbjs-genfiles/plugin';
+import * as fs from 'fs';
+import * as path from 'path';
 
 import { Naming } from './naming';
 import { Proto, MessagesMap, ResourceDescriptor, ResourceMap } from './proto';
-import { fstat } from 'fs-extra';
+
+const googleGaxLocation = path.dirname(require.resolve('google-gax'));
+const gaxProtosLocation = path.join(googleGaxLocation, '..', '..', 'protos');
 
 export interface ProtosMap {
   [filename: string]: Proto;
@@ -31,6 +35,7 @@ export class API {
     // parse resource map to Proto constructor
     this.protos = fileDescriptors
       .filter(fd => fd.name)
+      .filter(fd => !fs.existsSync(path.join(gaxProtosLocation, fd.name!)))
       .reduce(
         (map, fd) => {
           map[fd.name!] = new Proto(
diff --git a/typescript/test/unit/api.ts b/typescript/test/unit/api.ts
new file mode 100644
index 000000000..81a55eb0c
--- /dev/null
+++ b/typescript/test/unit/api.ts
@@ -0,0 +1,39 @@
+import { API } from '../../src/schema/api';
+import * as plugin from '../../../pbjs-genfiles/plugin';
+import * as assert from 'assert';
+
+describe('schema/api.ts', () => {
+  it('should construct an API object and return list of protos', () => {
+    const fd = new plugin.google.protobuf.FileDescriptorProto();
+    fd.name = 'google/cloud/test/v1/test.proto';
+    fd.package = 'google.cloud.test.v1';
+    fd.service = [new plugin.google.protobuf.ServiceDescriptorProto()];
+    const api = new API(
+      [fd],
+      'google.cloud.test.v1',
+      new plugin.grpc.service_config.ServiceConfig()
+    );
+    assert.deepStrictEqual(api.filesToGenerate, [
+      'google/cloud/test/v1/test.proto',
+    ]);
+  });
+
+  it('should not return common protos in the list of protos', () => {
+    const fd1 = new plugin.google.protobuf.FileDescriptorProto();
+    fd1.name = 'google/cloud/test/v1/test.proto';
+    fd1.package = 'google.cloud.test.v1';
+    fd1.service = [new plugin.google.protobuf.ServiceDescriptorProto()];
+    const fd2 = new plugin.google.protobuf.FileDescriptorProto();
+    fd2.name = 'google/longrunning/operation.proto';
+    fd2.package = 'google.longrunning';
+    fd2.service = [new plugin.google.protobuf.ServiceDescriptorProto()];
+    const api = new API(
+      [fd1, fd2],
+      'google.cloud.test.v1',
+      new plugin.grpc.service_config.ServiceConfig()
+    );
+    assert.deepStrictEqual(api.filesToGenerate, [
+      'google/cloud/test/v1/test.proto',
+    ]);
+  });
+});