diff --git a/src/entity.ts b/src/entity.ts
index 6eb43bf19..0deefa5fe 100644
--- a/src/entity.ts
+++ b/src/entity.ts
@@ -51,12 +51,15 @@ entity.KEY_SYMBOL = Symbol('KEY');
  * const datastore = new Datastore();
  * const aDouble = datastore.double(7.3);
  */
-function Double(value) {
-  /**
-   * @name Double#value
-   * @type {number}
-   */
-  this.value = value;
+class Double {
+  value: number;
+  constructor(value: number) {
+    /**
+     * @name Double#value
+     * @type {number}
+     */
+    this.value = value;
+  }
 }
 
 entity.Double = Double;
@@ -85,12 +88,15 @@ entity.isDsDouble = isDsDouble;
  * const datastore = new Datastore();
  * const anInt = datastore.int(7);
  */
-function Int(value) {
-  /**
-   * @name Int#value
-   * @type {string}
-   */
-  this.value = value.toString();
+class Int {
+  value: string;
+  constructor(value: number|string) {
+    /**
+     * @name Int#value
+     * @type {string}
+     */
+    this.value = value.toString();
+  }
 }
 
 entity.Int = Int;
@@ -108,6 +114,11 @@ function isDsInt(value) {
 
 entity.isDsInt = isDsInt;
 
+export interface Coordinates {
+  latitude: number;
+  longitude: number;
+}
+
 /**
  * Build a Datastore Geo Point object.
  *
@@ -126,16 +137,19 @@ entity.isDsInt = isDsInt;
  *
  * const geoPoint = datastore.geoPoint(coordinates);
  */
-function GeoPoint(coordinates) {
-  /**
-   * Coordinate value.
-   *
-   * @name GeoPoint#coordinates
-   * @type {object}
-   * @property {number} latitude Latitudinal value.
-   * @property {number} longitude Longitudinal value.
-   */
-  this.value = coordinates;
+class GeoPoint {
+  value: Coordinates;
+  constructor(coordinates: Coordinates) {
+    /**
+     * Coordinate value.
+     *
+     * @name GeoPoint#coordinates
+     * @type {object}
+     * @property {number} latitude Latitudinal value.
+     * @property {number} longitude Longitudinal value.
+     */
+    this.value = coordinates;
+  }
 }
 
 entity.GeoPoint = GeoPoint;
@@ -169,46 +183,55 @@ entity.isDsGeoPoint = isDsGeoPoint;
  *   path: ['Company', 123]
  * });
  */
-function Key(options) {
-  /**
-   * @name Key#namespace
-   * @type {string}
-   */
-  this.namespace = options.namespace;
-
-  options.path = [].slice.call(options.path);
-
-  if (options.path.length % 2 === 0) {
-    const identifier = options.path.pop();
-
-    if (is.number(identifier) || isDsInt(identifier)) {
-      this.id = identifier.value || identifier;
-    } else if (is.string(identifier)) {
-      this.name = identifier;
+class Key {
+
+  namespace: string;
+  id?: string;
+  name?: string;
+  kind: string;
+  parent?: Key;
+
+  constructor(options) {
+    /**
+     * @name Key#namespace
+     * @type {string}
+     */
+    this.namespace = options.namespace;
+
+    options.path = [].slice.call(options.path);
+
+    if (options.path.length % 2 === 0) {
+      const identifier = options.path.pop();
+
+      if (is.number(identifier) || isDsInt(identifier)) {
+        this.id = identifier.value || identifier;
+      } else if (is.string(identifier)) {
+        this.name = identifier;
+      }
     }
-  }
 
-  this.kind = options.path.pop();
+    this.kind = options.path.pop();
 
-  if (options.path.length > 0) {
-    this.parent = new Key(options);
-  }
+    if (options.path.length > 0) {
+      this.parent = new Key(options);
+    }
 
-  // `path` is computed on demand to consider any changes that may have been
-  // made to the key.
-  /**
-   * @name Key#path
-   * @type {array}
-   */
-  Object.defineProperty(this, 'path', {
-    enumerable: true,
-    get: function() {
-      return arrify(this.parent && this.parent.path).concat([
-        this.kind,
-        this.name || this.id,
-      ]);
-    },
-  });
+    // `path` is computed on demand to consider any changes that may have been
+    // made to the key.
+    /**
+     * @name Key#path
+     * @type {array}
+     */
+    Object.defineProperty(this, 'path', {
+      enumerable: true,
+      get: function() {
+        return arrify(this.parent && this.parent.path).concat([
+          this.kind,
+          this.name || this.id,
+        ]);
+      },
+    });
+  }
 }
 
 entity.Key = Key;
diff --git a/test/index.ts b/test/index.ts
index d293e33fc..56a8ee7bc 100644
--- a/test/index.ts
+++ b/test/index.ts
@@ -75,12 +75,18 @@ const fakeGoogleGax = {
   },
 };
 
-function FakeQuery() {
-  this.calledWith_ = arguments;
+class FakeQuery {
+  calledWith_: IArguments;
+  constructor() {
+    this.calledWith_ = arguments;
+  }
 }
 
-function FakeTransaction() {
-  this.calledWith_ = arguments;
+class FakeTransaction {
+  calledWith_: IArguments;
+  constructor() {
+    this.calledWith_ = arguments;
+  }
 }
 
 function FakeV1() {}
diff --git a/test/request.ts b/test/request.ts
index 473973bf3..53b1266e8 100644
--- a/test/request.ts
+++ b/test/request.ts
@@ -48,9 +48,7 @@ const fakeV1 = {
   },
 };
 
-function FakeQuery() {
-  this.calledWith_ = arguments;
-}
+class FakeQuery extends Query {}
 
 let pjyOverride;
 
@@ -59,7 +57,7 @@ describe('Request', function() {
   let request;
 
   let key;
-  let sandbox;
+  const sandbox = sinon.createSandbox();
 
   before(function() {
     Request = proxyquire('../src/request', {
@@ -71,25 +69,21 @@ describe('Request', function() {
     }).DatastoreRequest;
   });
 
-  after(function() {
+  after(() => {
     v1FakeClientOverride = null;
   });
 
   beforeEach(function() {
-    sandbox = sinon.createSandbox();
     pjyOverride = null;
     key = new entity.Key({
       namespace: 'namespace',
       path: ['Company', 123],
     });
-    FakeQuery.prototype = new Query();
     v1FakeClientOverride = null;
     request = new Request();
   });
 
-  afterEach(() => {
-    sandbox.restore();
-  });
+  afterEach(() => sandbox.restore());
 
   describe('instantiation', function() {
     it('should promisify all the things', function() {
@@ -474,7 +468,7 @@ describe('Request', function() {
         request
           .createReadStream(key)
           .on('error', done)
-          .on('data', function(entity) {
+          .on('data', entity => {
             assert.deepStrictEqual(entity, expectedResult);
           })
           .on('end', done)
@@ -484,19 +478,18 @@ describe('Request', function() {
       it('should not push more results if stream was ended', function(done) {
         let entitiesEmitted = 0;
 
-        request.request_ = function(config, callback) {
-          setImmediate(function() {
+        request.request_ = (config, callback) => {
+          setImmediate(() => {
             callback(null, apiResponseWithMultiEntities);
           });
         };
 
-        request
-          .createReadStream([key, key])
-          .on('data', function() {
+        const stream = request.createReadStream([key, key]);
+          stream.on('data', () => {
             entitiesEmitted++;
-            this.end();
+            stream.end();
           })
-          .on('end', function() {
+          .on('end', () => {
             assert.strictEqual(entitiesEmitted, 1);
             done();
           })
@@ -513,13 +506,11 @@ describe('Request', function() {
           });
         };
 
-        request
-          .createReadStream(key)
+        const stream = request.createReadStream(key);
+        stream
           .on('error', done)
-          .on('data', function() {
-            this.end();
-          })
-          .on('end', function() {
+          .on('data', () => stream.end())
+          .on('end', () => {
             assert.strictEqual(lookupCount, 1);
             done();
           })
@@ -930,16 +921,16 @@ describe('Request', function() {
           );
           startCalled = true;
           return this;
-        };
+        }
 
-        FakeQuery.prototype.offset = function(offset_) {
+        sandbox.stub(FakeQuery.prototype, 'offset').callsFake(offset_ => {
           const offset = query.offsetVal - apiResponse.batch.skippedResults;
           assert.strictEqual(offset_, offset);
           offsetCalled = true;
           return this;
-        };
+        });
 
-        FakeQuery.prototype.limit = function(limit_) {
+        sandbox.stub(FakeQuery.prototype, 'limit').callsFake(limit_ => {
           if (timesRequestCalled === 1) {
             assert.strictEqual(
               limit_,
@@ -950,7 +941,7 @@ describe('Request', function() {
             assert.strictEqual(limit_, query.limitVal);
           }
           return this;
-        };
+        });
 
         sandbox.stub(entity, 'queryToQueryProto').callsFake(query_ => {
           if (timesRequestCalled > 1) {
@@ -1012,10 +1003,10 @@ describe('Request', function() {
 
         sandbox.stub(entity, 'queryToQueryProto').returns({});
 
-        FakeQuery.prototype.limit = function() {
+        sandbox.stub(FakeQuery.prototype, 'limit').callsFake(() => {
           limitCalled = true;
           return this;
-        };
+        });
 
         request
           .runQueryStream(query)
@@ -1050,13 +1041,13 @@ describe('Request', function() {
           }
         };
 
-        request
+        const stream = request
           .runQueryStream({})
-          .on('data', function() {
+          .on('data', () => {
             entitiesEmitted++;
-            this.end();
+            stream.end();
           })
-          .on('end', function() {
+          .on('end', () => {
             assert.strictEqual(entitiesEmitted, 1);
             done();
           });
@@ -1070,13 +1061,11 @@ describe('Request', function() {
           callback(null, apiResponse);
         };
 
-        request
-          .runQueryStream({})
+        const stream = request.runQueryStream({});
+        stream
           .on('error', done)
-          .on('data', function() {
-            this.end();
-          })
-          .on('end', function() {
+          .on('data', () => stream.end())
+          .on('end', () => {
             assert.strictEqual(timesRequestCalled, 1);
             done();
           });
diff --git a/tsconfig.json b/tsconfig.json
index 1942ae08f..5dc9ad65f 100644
--- a/tsconfig.json
+++ b/tsconfig.json
@@ -3,8 +3,7 @@
   "compilerOptions": {
     "rootDir": ".",
     "outDir": "build",
-    "noImplicitAny": false,
-    "noImplicitThis": false
+    "noImplicitAny": false
   },
   "include": [
     "src/*.ts",