diff --git a/packages/datastore/src/transaction.js b/packages/datastore/src/transaction.js
index c28bbd0f56c..3a90c1c7f11 100644
--- a/packages/datastore/src/transaction.js
+++ b/packages/datastore/src/transaction.js
@@ -26,6 +26,12 @@ var flatten = require('lodash.flatten');
 var prop = require('propprop');
 var util = require('util');
 
+/**
+ * @type {module:datastore/entity}
+ * @private
+ */
+var entity = require('./entity.js');
+
 /**
  * @type {module:datastore/request}
  * @private
@@ -129,10 +135,16 @@ Transaction.prototype.commit = function(callback) {
     // key they just asked to be deleted, the delete request will be ignored,
     // giving preference to the save operation.
     .filter(function(modifiedEntity) {
-      var key = JSON.stringify(modifiedEntity.entity.key);
+      var key = modifiedEntity.entity.key;
+
+      if (!entity.isKeyComplete(key)) {
+        return true;
+      }
+
+      var stringifiedKey = JSON.stringify(modifiedEntity.entity.key);
 
-      if (!keys[key]) {
-        keys[key] = true;
+      if (!keys[stringifiedKey]) {
+        keys[stringifiedKey] = true;
         return true;
       }
     })
diff --git a/packages/datastore/test/transaction.js b/packages/datastore/test/transaction.js
index 263d54132f7..123ee58fd8e 100644
--- a/packages/datastore/test/transaction.js
+++ b/packages/datastore/test/transaction.js
@@ -261,6 +261,20 @@ describe('Transaction', function() {
       assert.equal(saveCalled, 1);
     });
 
+    it('should not squash key-incomplete mutations', function(done) {
+      transaction.save({ key: key(['Product']), data: '' });
+      transaction.save({ key: key(['Product']), data: '' });
+
+      DatastoreRequestOverride.save = function(entities) {
+        assert.strictEqual(entities.length, 2);
+        done();
+      };
+
+      transaction.request_ = util.noop;
+
+      transaction.commit();
+    });
+
     it('should send the built request object', function(done) {
       transaction.requests_ = [
         {