diff --git a/circle.yml b/circle.yml
index eeeb00653c..fbbc7ab8f3 100644
--- a/circle.yml
+++ b/circle.yml
@@ -20,6 +20,9 @@ dependencies:
     # We install and test with all the supported MongoDB versions
     - case $CIRCLE_NODE_INDEX in [1,2]) sudo service mongodb stop ; MONGODB_VERSION=3.2.12 sudo -E .circle/install-and-run-mongodb.sh > /tmp/mongodb-install.log 2>&1 ;; [3,4]) sudo service mongodb stop ; MONGODB_VERSION=3.4.2 sudo -E .circle/install-and-run-mongodb.sh > /tmp/mongodb-install.log 2>&1 ;; esac:
         background: true
+    # We sleep a bit to wait for the background process to start and script to
+    # finish
+    - case $CIRCLE_NODE_INDEX in [1,2]) sleep 10 ;; esac
     # Tail the logs so it's easier to see what is going on. Sadly when using "background: true"
     # whole output is ignored.
     - case $CIRCLE_NODE_INDEX in [1,2]) tail -50 /tmp/mongodb-install.log ;; [3,4]) tail -50 /tmp/mongodb-install.log ;; esac
diff --git a/st2common/st2common/models/db/__init__.py b/st2common/st2common/models/db/__init__.py
index c0be7d6705..e131d4ecdc 100644
--- a/st2common/st2common/models/db/__init__.py
+++ b/st2common/st2common/models/db/__init__.py
@@ -118,6 +118,17 @@ def db_ensure_indexes():
 
         try:
             model_class.ensure_indexes()
+        except OperationFailure as e:
+            # Special case for "uid" index. MongoDB 3.4 has dropped "_types" index option so we
+            # need to re-create the index to make it work and avoid "index with different options
+            # already exists" error.
+            # Note: This condition would only be encountered when upgrading existing StackStorm
+            # installation from MongoDB 3.2 to 3.4.
+            msg = str(e)
+            if 'already exists with different options' in msg and 'uid_1' in msg:
+                drop_obsolete_types_indexes(model_class=model_class)
+            else:
+                raise e
         except Exception as e:
             tb_msg = traceback.format_exc()
             msg = 'Failed to ensure indexes for model "%s": %s' % (class_name, str(e))
@@ -157,6 +168,32 @@ def cleanup_extra_indexes(model_class):
     return removed_count
 
 
+def drop_obsolete_types_indexes(model_class):
+    """
+    Special class for droping offending "types" indexes for which support has
+    been removed in mongoengine and MongoDB 3.4.
+    For more info, see: http://docs.mongoengine.org/upgrade.html#inheritance
+    """
+    class_name = model_class.__name__
+
+    LOG.debug('Dropping obsolete types index for model "%s"' % (class_name))
+    collection = model_class._get_collection()
+    collection.update({}, {'$unset': {'_types': 1}}, multi=True)
+
+    info = collection.index_information()
+    indexes_to_drop = [key for key, value in info.iteritems()
+                       if '_types' in dict(value['key']) or 'types' in value]
+
+    LOG.debug('Will drop obsolete types indexes for model "%s": %s' % (class_name,
+                                                                       str(indexes_to_drop)))
+
+    for index in indexes_to_drop:
+        collection.drop_index(index)
+
+    LOG.debug('Recreating indexes for model "%s"' % (class_name))
+    model_class.ensure_indexes()
+
+
 def db_teardown():
     mongoengine.connection.disconnect()