diff --git a/lib/datastore/dataset.js b/lib/datastore/dataset.js
index 163ca353343..ee5f0b7a779 100644
--- a/lib/datastore/dataset.js
+++ b/lib/datastore/dataset.js
@@ -37,11 +37,7 @@ var SCOPES = [
  */
 function Dataset(opts) {
   opts = opts || {};
-  var id = opts.projectId || '';
-
-  if (id.indexOf('s~') === -1 && id.indexOf('e~') === -1) {
-    id = 's~' + id;
-  }
+  var id = opts.projectId;
 
   this.connection = new conn.Connection({
     keyFilename: opts.keyFilename,
@@ -109,7 +105,7 @@ Dataset.prototype.allocateIds = function(incompleteKey, n, callback) {
   }
   var incompleteKeys = [];
   for (var i = 0; i < n; i++) {
-    incompleteKeys.push(entity.keyToKeyProto(this.id, incompleteKey));
+    incompleteKeys.push(entity.keyToKeyProto(incompleteKey));
   }
   this.transaction.makeReq(
       'allocateIds', { keys: incompleteKeys }, function(err, resp) {
diff --git a/lib/datastore/entity.js b/lib/datastore/entity.js
index 11a71d82b1e..e0b1bcbefc8 100644
--- a/lib/datastore/entity.js
+++ b/lib/datastore/entity.js
@@ -91,7 +91,7 @@ var keyFromKeyProto = function(proto) {
 
 module.exports.keyFromKeyProto = keyFromKeyProto;
 
-var keyToKeyProto = function(datasetId, key) {
+var keyToKeyProto = function(key) {
   if (key.length < 2) {
     throw new Error('A key should contain at least a kind and an identifier.');
   }
@@ -120,12 +120,9 @@ var keyToKeyProto = function(datasetId, key) {
     path: path
   };
   if (namespace) {
-    proto.partitionId = {};
-    proto.partitionId.namespace = namespace;
-  }
-  if (datasetId) {
-    proto.partitionId = proto.partitionId || {};
-    proto.partitionId.datasetId = datasetId;
+    proto.partitionId = {
+      namespace: namespace
+    };
   }
   return proto;
 };
@@ -142,7 +139,7 @@ module.exports.formatArray = function(results) {
 };
 
 module.exports.isKeyComplete = function(key) {
-  var proto = keyToKeyProto(null, key);
+  var proto = keyToKeyProto(key);
   for (var i = 0; i < proto.path.length; i++) {
     if (!proto.path[i].kind) {
       return false;
@@ -284,7 +281,7 @@ var queryToQueryProto = function(q) {
     var filters = q.filters.map(function(f) {
       var val = {};
       if (f.name === '__key__') {
-        val.keyValue = keyToKeyProto(null, f.val);
+        val.keyValue = keyToKeyProto(f.val);
       } else {
         val = valueToProperty(f.val);
       }
diff --git a/lib/datastore/transaction.js b/lib/datastore/transaction.js
index 54dea3c0d18..bbcb7c3593c 100644
--- a/lib/datastore/transaction.js
+++ b/lib/datastore/transaction.js
@@ -104,7 +104,7 @@ Transaction.prototype.get = function(keys, callback) {
   keys = isMultipleRequest ? keys : [keys];
   callback = callback || util.noop;
   var req = {
-    keys: keys.map(entity.keyToKeyProto.bind(null, this.id))
+    keys: keys.map(entity.keyToKeyProto)
   };
   if (this.id) {
     req.transaction = this.id;
@@ -137,7 +137,7 @@ Transaction.prototype.save = function(entities, callback) {
     mode: MODE_NON_TRANSACTIONAL,
     mutation: entities.reduce(function(acc, entityObject, index) {
       var ent = entity.entityToEntityProto(entityObject.data);
-      ent.key = entity.keyToKeyProto(this.datasetId, entityObject.key);
+      ent.key = entity.keyToKeyProto(entityObject.key);
       if (entity.isKeyComplete(entityObject.key)) {
         acc.upsert.push(ent);
       } else {
@@ -176,7 +176,7 @@ Transaction.prototype.delete = function(keys, callback) {
   var req = {
     mode: MODE_NON_TRANSACTIONAL,
     mutation: {
-      delete: keys.map(entity.keyToKeyProto.bind(null, this.id))
+      delete: keys.map(entity.keyToKeyProto)
     }
   };
   if (this.id) {
diff --git a/test/datastore/dataset.js b/test/datastore/dataset.js
index 4977a71b28a..305a6d19a53 100644
--- a/test/datastore/dataset.js
+++ b/test/datastore/dataset.js
@@ -24,16 +24,6 @@ var mockRespGet = require('../testdata/response_get.json');
 var Transaction = require('../../lib/datastore/transaction.js');
 
 describe('Dataset', function() {
-  it('should append ~s if ~s or ~e are not presented', function(done) {
-    var dsWithNoPrefix = new datastore.Dataset({ projectId: 'test' });
-    var dsWithSPrefix = new datastore.Dataset({ projectId: 's~name' });
-    var dsWithEPrefix = new datastore.Dataset({ projectId: 'e~name' });
-    assert.equal(dsWithNoPrefix.id, 's~test');
-    assert.equal(dsWithSPrefix.id, 's~name');
-    assert.equal(dsWithEPrefix.id, 'e~name');
-    done();
-  });
-
   it('should get by key', function(done) {
     var ds = new datastore.Dataset({ projectId: 'test' });
     ds.transaction.makeReq = function(method, proto, callback) {
@@ -126,9 +116,6 @@ describe('Dataset', function() {
       assert.equal(method, 'allocateIds');
       assert.equal(proto.keys.length, 1);
       assert.deepEqual(proto.keys[0], {
-        partitionId:{
-          datasetId: 's~test',
-        },
         path :[{kind:'Kind'}]
       });
       callback(null, {
diff --git a/test/datastore/entity.js b/test/datastore/entity.js
index 324cc3dedb5..224f23d83ae 100644
--- a/test/datastore/entity.js
+++ b/test/datastore/entity.js
@@ -169,9 +169,8 @@ describe('keyFromKeyProto', function() {
 describe('keyToKeyProto', function() {
   it('should handle hierarchical key definitions', function(done) {
     var key = ['Kind1', 1, 'Kind2', 'name'];
-    var proto = entity.keyToKeyProto('datasetId', key);
-    assert.strictEqual(proto.partitionId.datasetId, 'datasetId');
-    assert.strictEqual(proto.partitionId.namespace, undefined);
+    var proto = entity.keyToKeyProto(key);
+    assert.strictEqual(proto.partitionId, undefined);
     assert.strictEqual(proto.path[0].kind, 'Kind1');
     assert.strictEqual(proto.path[0].id, 1);
     assert.strictEqual(proto.path[0].name, undefined);
@@ -183,8 +182,7 @@ describe('keyToKeyProto', function() {
 
   it('should detect the namespace of the hierarchical keys', function(done) {
     var key = ['Namespace', 'Kind1', 1, 'Kind2', 'name'];
-    var proto = entity.keyToKeyProto('datasetId', key);
-    assert.strictEqual(proto.partitionId.datasetId, 'datasetId');
+    var proto = entity.keyToKeyProto(key);
     assert.strictEqual(proto.partitionId.namespace, 'Namespace');
     assert.strictEqual(proto.path[0].kind, 'Kind1');
     assert.strictEqual(proto.path[0].id, 1);
@@ -199,16 +197,14 @@ describe('keyToKeyProto', function() {
     var key = ['Kind1', null];
     var keyWithNS = ['Namespace', 'Kind1', null];
 
-    var proto = entity.keyToKeyProto('datasetId', key);
-    var protoWithNS = entity.keyToKeyProto('datasetId', keyWithNS);
+    var proto = entity.keyToKeyProto(key);
+    var protoWithNS = entity.keyToKeyProto(keyWithNS);
 
-    assert.strictEqual(proto.partitionId.datasetId, 'datasetId');
-    assert.strictEqual(proto.partitionId.namespace, undefined);
+    assert.strictEqual(proto.partitionId, undefined);
     assert.strictEqual(proto.path[0].kind, 'Kind1');
     assert.strictEqual(proto.path[0].id, undefined);
     assert.strictEqual(proto.path[0].name, undefined);
 
-    assert.strictEqual(protoWithNS.partitionId.datasetId, 'datasetId');
     assert.strictEqual(protoWithNS.partitionId.namespace, 'Namespace');
     assert.strictEqual(protoWithNS.path[0].kind, 'Kind1');
     assert.strictEqual(protoWithNS.path[0].id, undefined);
@@ -218,7 +214,7 @@ describe('keyToKeyProto', function() {
 
   it('should throw if key contains less than 2 items', function() {
     assert.throws(function() {
-      entity.keyToKeyProto('datasetId', ['Kind']);
+      entity.keyToKeyProto(['Kind']);
     });
   });
 });