diff --git a/src/index.ts b/src/index.ts
index 101d9b371..a6b7771b4 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -45,6 +45,8 @@ import {BatchPublishOptions} from './publisher';
 const opts = {} as gax.GrpcClientOptions;
 const {grpc} = new gax.GrpcClient(opts);
 
+export type SeekCallback = RequestCallback<google.pubsub.v1.ISeekResponse>;
+
 export interface GetSubscriptionMetadataCallback {
   (err: ServiceError|null, res?: google.pubsub.v1.Subscription|null): void;
 }
diff --git a/src/publisher.ts b/src/publisher.ts
index e600beb63..3ffe3d5f8 100644
--- a/src/publisher.ts
+++ b/src/publisher.ts
@@ -24,15 +24,22 @@ import * as extend from 'extend';
 import * as is from 'is';
 import {Topic} from './topic';
 import {RequestCallback, Attributes} from '.';
+import {ServiceError} from 'grpc';
 
 interface Inventory {
-  callbacks: Array<RequestCallback<string>>;
-  queued: Array<{}>;
+  callbacks: QueueCallback[];
+  queued: google.pubsub.v1.IPubsubMessage[];
   bytes: number;
 }
 
 export interface PublishCallback {
-  (err?: null|Error, messageId?: string|null): void;
+  (err: ServiceError, messageId?: null): void;
+  (err: null, messageId: string): void;
+}
+
+interface QueueCallback {
+  (err: ServiceError, res?: null): void;
+  (err: null, res: string): void;
 }
 
 /**
@@ -284,9 +291,8 @@ export class Publisher {
    * @param {function} callback The callback function.
    */
   queue_(data: Buffer, attrs: Attributes): Promise<string>;
-  queue_(data: Buffer, attrs: Attributes, callback: RequestCallback<string>):
-      void;
-  queue_(data: Buffer, attrs: Attributes, callback?: RequestCallback<string>):
+  queue_(data: Buffer, attrs: Attributes, callback: QueueCallback): void;
+  queue_(data: Buffer, attrs: Attributes, callback?: QueueCallback):
       void|Promise<string> {
     this.inventory_.queued.push({
       data,
diff --git a/src/snapshot.ts b/src/snapshot.ts
index 2562b8f48..57e4c6bd1 100644
--- a/src/snapshot.ts
+++ b/src/snapshot.ts
@@ -16,8 +16,10 @@
 
 import {promisifyAll} from '@google-cloud/promisify';
 import {CallOptions} from 'google-gax';
+
 import {google} from '../proto/pubsub';
-import {CreateSnapshotCallback, CreateSnapshotResponse, RequestCallback, Subscription} from '.';
+
+import {CreateSnapshotCallback, CreateSnapshotResponse, RequestCallback, SeekCallback, Subscription} from '.';
 import {PubSub} from './index';
 import * as util from './util';
 
@@ -126,14 +128,13 @@ export class Snapshot {
       snapshot: this.name,
     };
     callback = callback || util.noop;
-    (this.parent as PubSub)
-        .request<google.protobuf.Empty>(
-            {
-              client: 'SubscriberClient',
-              method: 'deleteSnapshot',
-              reqOpts,
-            },
-            callback);
+    this.parent.request<google.protobuf.Empty>(
+        {
+          client: 'SubscriberClient',
+          method: 'deleteSnapshot',
+          reqOpts,
+        },
+        callback);
   }
   /*@
    * Format the name of a snapshot. A snapshot's full name is in the format of
@@ -153,23 +154,21 @@ export class Snapshot {
       gaxOpts?: CallOptions|CreateSnapshotCallback,
       callback?: CreateSnapshotCallback): void|Promise<CreateSnapshotResponse> {
     if (!(this.parent instanceof Subscription)) {
-      throw new Error(`Subscription#snapshot`);
+      throw new Error(
+          `This is only available if you accessed this object through Subscription#snapshot`);
     }
     return (this.parent as Subscription)
         .createSnapshot(this.name, gaxOpts! as CallOptions, callback!);
   }
 
   seek(gaxOpts?: CallOptions): Promise<google.pubsub.v1.SeekResponse>;
-  seek(callback: google.pubsub.v1.Subscriber.SeekCallback): void;
-  seek(
-      gaxOpts: CallOptions,
-      callback: google.pubsub.v1.Subscriber.SeekCallback): void;
-  seek(
-      gaxOpts?: CallOptions|google.pubsub.v1.Subscriber.SeekCallback,
-      callback?: google.pubsub.v1.Subscriber.SeekCallback):
+  seek(callback: SeekCallback): void;
+  seek(gaxOpts: CallOptions, callback: SeekCallback): void;
+  seek(gaxOpts?: CallOptions|SeekCallback, callback?: SeekCallback):
       void|Promise<google.pubsub.v1.SeekResponse> {
     if (!(this.parent instanceof Subscription)) {
-      throw new Error(`Subscription#snapshot`);
+      throw new Error(
+          `This is only available if you accessed this object through Subscription#snapshot`);
     }
     return (this.parent as Subscription)
         .seek(this.name, gaxOpts! as CallOptions, callback!);
diff --git a/src/subscription.ts b/src/subscription.ts
index 61fe4d8e1..3d41bc479 100644
--- a/src/subscription.ts
+++ b/src/subscription.ts
@@ -20,8 +20,10 @@ import * as extend from 'extend';
 import {CallOptions} from 'google-gax';
 import * as is from 'is';
 import * as snakeCase from 'lodash.snakecase';
+
 import {google} from '../proto/pubsub';
-import {CreateSnapshotCallback, CreateSnapshotResponse, CreateSubscriptionCallback, CreateSubscriptionResponse, ExistsCallback, GetCallOptions, GetSubscriptionMetadataCallback, Metadata, PubSub, RequestCallback, SubscriptionCallOptions} from '.';
+
+import {CreateSnapshotCallback, CreateSnapshotResponse, CreateSubscriptionCallback, CreateSubscriptionResponse, ExistsCallback, GetCallOptions, GetSubscriptionMetadataCallback, Metadata, PubSub, RequestCallback, SeekCallback, SubscriptionCallOptions} from '.';
 import {IAM} from './iam';
 import {Snapshot} from './snapshot';
 import {Subscriber, SubscriberOptions} from './subscriber';
@@ -201,7 +203,7 @@ export class Subscription extends EventEmitter {
   name: string;
 
   metadata: Metadata;
-  request: Function;
+  request: typeof PubSub.prototype.request;
   private _subscriber: Subscriber;
   constructor(pubsub: PubSub, name: string, options?: SubscriptionCallOptions) {
     super();
@@ -209,7 +211,8 @@ export class Subscription extends EventEmitter {
     options = options || {};
 
     this.pubsub = pubsub;
-    this.request = pubsub.request.bind(pubsub);
+    // tslint:disable-next-line no-any
+    this.request = pubsub.request.bind(pubsub) as any;
     this.name = Subscription.formatName_(this.projectId, name);
 
     if (options.topic) {
@@ -365,20 +368,20 @@ export class Subscription extends EventEmitter {
       name: snapshot.name,
       subscription: this.name,
     };
-    this.request(
+    this.request<google.pubsub.v1.Snapshot>(
         {
           client: 'SubscriberClient',
           method: 'createSnapshot',
           reqOpts,
           gaxOpts,
         },
-        (err: Error, resp: google.pubsub.v1.Snapshot) => {
+        (err, resp) => {
           if (err) {
-            callback!(err, null, resp);
+            callback!(err, null, resp!);
             return;
           }
-          snapshot.metadata = resp;
-          callback!(null, snapshot, resp);
+          snapshot.metadata = resp!;
+          callback!(null, snapshot, resp!);
         });
   }
   /**
@@ -610,18 +613,18 @@ export class Subscription extends EventEmitter {
     const reqOpts = {
       subscription: this.name,
     };
-    this.request(
+    this.request<google.pubsub.v1.Subscription>(
         {
           client: 'SubscriberClient',
           method: 'getSubscription',
           reqOpts,
           gaxOpts,
         },
-        (err: Error, apiResponse: google.pubsub.v1.Subscription) => {
+        (err, apiResponse) => {
           if (!err) {
             this.metadata = apiResponse;
           }
-          callback!(err, apiResponse);
+          callback!(err!, apiResponse);
         });
   }
   /**
@@ -700,7 +703,7 @@ export class Subscription extends EventEmitter {
           reqOpts,
           gaxOpts,
         },
-        callback);
+        callback!);
   }
   /**
    * Opens the Subscription to receive messages. In general this method
@@ -767,17 +770,12 @@ export class Subscription extends EventEmitter {
    */
   seek(snapshot: string|Date, gaxOpts?: CallOptions):
       Promise<google.pubsub.v1.SeekResponse>;
+  seek(snapshot: string|Date, callback: SeekCallback): void;
+  seek(snapshot: string|Date, gaxOpts: CallOptions, callback: SeekCallback):
+      void;
   seek(
-      snapshot: string|Date,
-      callback: google.pubsub.v1.Subscriber.SeekCallback): void;
-  seek(
-      snapshot: string|Date, gaxOpts: CallOptions,
-      callback: google.pubsub.v1.Subscriber.SeekCallback): void;
-  seek(
-      snapshot: string|Date,
-      gaxOptsOrCallback?: CallOptions|google.pubsub.v1.Subscriber.SeekCallback,
-      callback?: google.pubsub.v1.Subscriber.SeekCallback):
-      void|Promise<google.pubsub.v1.SeekResponse> {
+      snapshot: string|Date, gaxOptsOrCallback?: CallOptions|SeekCallback,
+      callback?: SeekCallback): void|Promise<google.pubsub.v1.SeekResponse> {
     const gaxOpts =
         typeof gaxOptsOrCallback === 'object' ? gaxOptsOrCallback : {};
     callback =
@@ -809,7 +807,7 @@ export class Subscription extends EventEmitter {
           reqOpts,
           gaxOpts,
         },
-        callback);
+        callback!);
   }
   /**
    * @typedef {array} SetSubscriptionMetadataResponse
@@ -882,7 +880,7 @@ export class Subscription extends EventEmitter {
           reqOpts,
           gaxOpts,
         },
-        callback);
+        callback!);
   }
   /**
    * Sets the Subscription options.
diff --git a/test/snapshot.ts b/test/snapshot.ts
index 4ca24cd12..edc63a530 100644
--- a/test/snapshot.ts
+++ b/test/snapshot.ts
@@ -155,11 +155,15 @@ describe('Snapshot', () => {
       });
 
       it('should throw on create method', () => {
-        assert.throws(() => snapshot.create(), /Subscription#snapshot/);
+        assert.throws(
+            () => snapshot.create(),
+            /This is only available if you accessed this object through Subscription#snapshot/);
       });
 
       it('should throw on seek method', () => {
-        assert.throws(() => snapshot.seek(), /Subscription#snapshot/);
+        assert.throws(
+            () => snapshot.seek(),
+            /This is only available if you accessed this object through Subscription#snapshot/);
       });
     });
   });