diff --git a/packages/minimongo/local_collection.js b/packages/minimongo/local_collection.js
index 4366d65645..ac14703cc8 100644
--- a/packages/minimongo/local_collection.js
+++ b/packages/minimongo/local_collection.js
@@ -660,6 +660,22 @@ export default class LocalCollection {
 
     this._observeQueue.drain();
 
+
+    // If we are doing an upsert, and we didn't modify any documents yet, then
+    // it's time to do an insert. Figure out what document we are inserting, and
+    // generate an id for it.
+    let insertedId;
+    if (updateCount === 0 && options.upsert) {
+      const doc = LocalCollection._createUpsertDocument(selector, mod);
+      if (!doc._id && options.insertedId) {
+        doc._id = options.insertedId;
+      }
+
+      insertedId = this.insert(doc);
+      updateCount = 1;
+    }
+
+
     return this.finishUpdate({
       options,
       updateCount,
diff --git a/packages/minimongo/minimongo_tests_client.js b/packages/minimongo/minimongo_tests_client.js
index fd14e99fa4..2546316119 100644
--- a/packages/minimongo/minimongo_tests_client.js
+++ b/packages/minimongo/minimongo_tests_client.js
@@ -212,6 +212,21 @@ Tinytest.addAsync('minimongo - basics', async test => {
   test.equal(after.d, undefined);
 });
 
+
+Tinytest.addAsync('minimongo - upsert', async test => {
+  const c = new LocalCollection();
+
+  await c.upsertAsync({ name: 'doc' }, { name: 'doc' });
+  
+  test.equal(c.find({}).count(), 1);
+
+  await c.removeAsync({});
+
+  c.upsert({ name: 'doc' }, { name: 'doc' });
+  test.equal(c.find({}).count(), 1);
+});
+
+
 Tinytest.add('minimongo - error - no options', test => {
   try {
     throw MinimongoError('Not fun to have errors');